Volvo did have some soft camshafts and IIRC, there was a recall back in the day.
However, new cams shouldn't have this problem.
The cause of excessive wear nowadays is usually due to the low levels of ZDDP(Zinc and Phosphorous) in over the counter multi-weight oils. We suggest using 30w engine oil as the levels of ZDDP are allowed to be higher. We use Napa Premium 30w as it made by the same company that makes Valvoline and it's cheaper than Valvoline.
We recently replaced the cam in 544 whose owner is a loyal Rotella oil user and we found a significant amount of wear and pitting on most of the lifters. We used 30w VR1, a high ZDDP oil made by Valvoline, in his motor along with a high ZDDP lube on the camshaft lobes and lifters. Normally we switch back to 30w after that, but the owner wants to use 10w-40, so I suggested a ZDDP additive or to use VR1 10w-40.
For a longer life, it is extremely critical to break in a new camshaft and lifters by running the engine at 2000-3000 rpm for at least 15 minutes during the initial start up.
Lately, we've been suggesting to customers engine removal when replacing a camshaft for pushrod Volvo engines.
With the engine removed, you don't have to remove the head to change the camshaft.
Since the oil pan gasket almost always tears when removing the front timing cover, with the engine removed the oil pan gasket has to be changed. A gasket patch can be used and glued in place, but it can still leak.
While the oil pan is off, the main and rod bearings can be inspected or changed if necessary as well as the oil pump and oil pump seals.
With the engine removed, you have access to the back of the motor so you can get to the rear main seal and the cam plug. And if your cam bearings are bad, it's way easier to have them changed with the engine removed.