As is often the case, YMMV.
I bought my present boat in 1994 with 3000 hrs on its TMD40A Volvos. in 2000 I repowered with TAMD41s with 1500 hrs. In that time I have added 3200 hrs. I have not experienced any issues whatsoever with parts availability or support from Volvo.
Perhaps the difference is that I have a former client who is a Volvo Penta dealer in Port Moody BC, He has no trouble whatsoever finding whatever he needs to find, either from the local Volvo warehouse, or from elsewhere.
My purchase of the 41s in 2000 illustrates the support one can get from VP: a Commander 30, powered originally with my 41s, couldn't get from Vancouver to Bamfield quickly enough to satisfy its original owner, who blamed the engines. After examining his complaints for a while, VP offered him an upgrade from 200hp engines to 235 hp engines. This was done, and the 41s were removed from the boat and sold off. I was in the right place at the right time, and though I didn't need newer engines, I took the plunge and haven't looked back. VP lost a bunch of $ on that deal, but demonstrated a high level of support to their customer. I don't know of anyone who has tried to get support for an older VP engine in my area and failed. My son recently purchased a 1987 boat with a VP 2001 (the model, not the year) sailboat engine. He had an exhaust elbow failure last summer and had no trouble getting a replacement immediately.