I check valve clearances when I do a timing belt change. If more than a couple are out of range, I simple measure and record all of them carefully, then I remove the camshaft - takes five minutes if the belt is already off. That allows me to replace the dampers on top of the retainers, and do the valve adjustment without any special tools. I can then polish the seal surface on the cam as well and ensure no leaks. Although Volvo advises to not reuse valve shims, I do stock used ones, and new ones. In Canada they wholesale at about $3.50 each, sell for $5.00, available new as an aftermarket part. The dealer does charge a lot more.

You could rent the IPD shim kit that charges you for the shims used but I think it really pays if you have a few cars to do. We usually take a group approach because a car can be done in 30 minutes or so once you get things going. Another method is to build a shim collection of your own but you have to swap cams, visit junkyards and swap heads to get that started. On the other hand, you are probably going about it the right way and should not have to do it that often, right? It seems like most do it once in the 100-200K miles range.