Many people (including myself) are buying vintage bows on Ebay and putting them back into service.  I wrote this guide to help people use these irreplacable artifacts without breaking them.  My grandfather was a golden age bowyer and many of these heirloom bows were broken by family members with the best of intentions and incomplete understanding of wooden bows!  After receiving your bow, do not string it immediately!  Let it sit for at least a few days to adjust to local humidity levels.  Fiberglass and laminated bows are much less affected by hunidity levels.  Take this time to make a tillering stick.  This is essentially a board with a notch cut in the end for the handle of the bow and notches cut along the length at various draw lengths.  Mine is made from a scrap 2" by 3" about 30 inches long.  This allows you to gradually increase the tension on the bow and hold it at a particular draw length.  Also make a tillering string.  This is a reinforced bowstring, extra long, with only one loop.  It allows you to string the bow without flexing it.  After your bow has adjusted to relative humidity levels, follow this advice directly plagiarized from The Traditional Bowyer's Bible vol. II. 

"USING OLD BOWS"
"Paul Comstock's comments on this subject:
    Increasing interest in wooden bows has led a number of archers to attempt to use wooden bows that are at least 40 years old.  If a wooden bow has not been used for 30 or 40 years, stringing it and immediately pulling it to full draw can easily make the bow explode into several pieces.  I have examined the wreckage to two such attempts.  Such disasters are particularly sad because an artifact from the pre-fiberglass era - an artifact that cannot be replaced - is destroyed.  Old lemonwood bows are the type most likely to break this way, even if they are backed.  Old Osage orange self bows are perhaps a bit tougher, but they too can be damaged.  The first full draw in 40 or 50 years can crack or splinter the back around a knot or pin.
    A really good wooden bow is one that performs well when it is thoroughly broken in.  Strain in the back of such a bow is reduced because the compacted wood of the belly provides nominal resistance.  When a wooden bow sits unused for 30 or 40 years, much of the natural compaction of the belly has been lost.  This means the wood in the belly is providing a proportionately higher level of resistance.  This greatly increases the odds of damage or fracture.
    It is possible to return an old wooden bow to service.  First examine it carefully.  See that the backing, if any, is in good shape and has no loose or missing spots.  If the bow has a handle riser, examine it to make sure the glue lines are still solid.  If the bow is unbacked, examine the back for cracks or other signs of damage.
    If the old bow is in excellent condition, string it about 5 or 6 inches high.  Once the old bow is strung, let it sit strung for six to eight hours.  Then unstring it.  Repeat the process a second and third day.  String it a fourth day and pull it to half-draw 100 or 200 times.  Then gradually increase the draw.
    During this process, constantly check the old bow for any signs of damage, and listen for cracking noises.  If there is no damage or cracking noise, odds are high the old bow can confidently used.
    This process can gradually and safely return the normal level of compaction to the bow's belly.  If this is done, the belly is providing a safe level of resistance and strain on the back is greatly reduced.  The danger of fracture or back damage falls dramatically.
    The finish on many old bows will be in bad shape.  The bow's historical value will be reduced if it is sanded clean and refinished.  If the bow is not to be refinished, the safest practice would be to keep the old bow waxed and never use it in wet weather."

Many of the vintage bows on Ebay are lemonwood (which is now known in woodworking circles as degame).   An additional note from The Traditional Bowyer's Bible vol. I:

   " Because lemonwood is so dense, it is extremely unlikely it would pull up a splinter in an unbacked bow.  My experience is if pulled too far, the unbacked lemonwood bow will blow apart without warning.  Lemonwood bows are rugged and highly durable unless the grain is severly tested.  When it is, the party's over....Many old books warn against drawing the wooden bow with no arrow on the string.  The writers were probably thinking of lemonwood when they wrote this.  Old lemonwood target and hunting bows were usually backed.  I own one with a fiber backing.  These backings were probably designed to minimize damage if the bow ever blew apart."  - Paul Comstock

So how far can you draw it? A rule of thumb is not longer than half of the length of the bow.  So for a 48" bow, no more than 24 inches, a 60" bow not more than 30 inches.  Of course, the older and rarer the bow, the more careful you should be.  Even the pros won't draw some historic bows.  Better safe than sorry!

I hope this guide has helped, good luck, good shooting, God bless

Quotations are copyright 2000 the Lyons Press and are used without permission, which is probably ok because the authors are a great bunch of folks and don't want to see old bows wrecked any more than I do, so unless the publishers are a big bunch of sticks in the mud, they'll forgive this infringement especially because The Traditional Bowyer's Bible volumes I, II, and III, are really great books that every traditional archer should own, I recommend them all the time, own copies, etc....plus they didn't ask my Grandma about any copyright infringement before putting photos of his bows in the series, so there!