I'm not coming down on either side of this issue - both sides make good points. I can only speak from my experience. I have never had a magazine spring fail on any pistol I've ever been issued, owned, used, or seen. Back in the 1980s my uncle produced several 1911 magazines that had been loaded since WW II. We unloaded them and cleaned them up then took them to the range for some 1911 fun. There were a couple of FTEs but no FTFs. These mags had been sitting for ~37 years fully loaded and they still worked. I think today's springs are better than those of WW II and as such I'm sure they will last at least as long if not longer.
That said; repeated compression and decompression (as in a lot of shooting) will wear out a spring. Some magazines are much harder to load the first few times but loosen up over time so springs do take a set or break in. Down loading by one round would seem like a good idea if a spring’s tension could change over time – just sitting or through repeated use.
Bottom line here is do what you want. It may or may not make a difference.