I wouldn't say Martin was using lesser quality limbs on previous bows. They had very good laminated limbs that sadly just wouldn't handle the stress put on them by the present cams. Most of the limb problems were prior to 2010. In 2010 they redesigned the limbs and went from 3 laminations to 4 which still didn't solve the problems totally. For 2011 they started using solid core limbs which seem to be holding up quite well.
All the older limbs were marked with deflection numbers such as 3M or 5M, a 2 number system. Solid core limbs are marked near the butt end with a 3 number deflection code such as 3MP, P standing for Power Tuff. If your bow has these then you're up to date. If your bow has the older limbs there still may not be any problems. They may last a long time, but if you should incur any limb problems then Martin will replace them with the newer limbs.
Hope this help allay any fears on your part. Enjoy your bow and hopefully you won't need to see how good customer service is.
If You're Not Living on the Edge You're Taking Up Too Much Space
Martin/Rytera Staff Shooter
PSAA Life member, UBP Life member
PADI AOW Diver