I would agree with this but I would add (totally subjectively) that I prefer the tone of broken-in XLs to that of broken-in Boomers so the way I would have described it is “Boomers go dead faster” even though we’re actually saying exactly the same thing from two different perspectives.I would also say that the XL’s gradually ease into their “played in” tone, whereas the Boomers go fast, almost overnight, but if you like their settled tone (most Boomer fans really do) they’ll stay that way longer.
Boomers were the first strings I ever used, followed by Roto-Sounds (which died even faster), then a few years with Dean Markleys and then I settled on D’Aquisto nickels as my Go-To strings. That worked great until D’Aquisto went belly-up and then I tried every freakin’ thing I could get my hands on and ended up liking the XLs the best.
For different degrees of warmer sounds I’ve had good luck with DR Sunbeams, R. Cocco and Sfarzo strings - all because I like the way they break in. The Sunbeams are by far the warmest and also much more flexible than the others. The Sfarzos are very nice and I’m not quite sure why they’re not more popular.