I bought a Makita two battery strimmer/brush cutter last year, mainly to tackle brambles. I chose Makita partly because I'm a tradesman and I use Makita 18 volt Li-Ion battery packs on an almost daily basis, so I could take some of my work batteries home to use. I average around 5 years lifespan out of a battery pack, more or less, but certainly never less than 4 years (I currently have 10 no 18 volt 5Ah batteries having killed off a further 8 over the last 14 or so years). This is a far better life span than the old NiCd and NIMH battery packs we used to have 15 years ago or more, but as all batteries do deteriorate over time I sincerely doubt that you'd get 10 years out of any battery on the market, and if you buy cordless you need to factor this in.
Another big improvement is that not only are modern battery packs smaller and lighter (a modern 18 volt 5 or 6Ah Li-Ion battery pack is some 1/3 smaller and 1/3 lighter than an earlier 18 volt 3.0Ah NiCd pack, so has maybe 2-1/2 times the energy density) but also modern Li-Ion-powered tools are going over to brushless motor technology, which means more power and greater run time. As
@wgt52 says, Li-Ion battery packs don't like the cold (I have prematurely killed battery packs by leaving them in the van over a weekend in freezing weather) so they can't ever be left to overwinter in a freezing cold shed or garage, so they must be brought indoors and the charge level checked periodically.
From my point of view the current generation of power garden tools (Li-Ion and brushless motors) are streets ahead of what you could buy 10 years ago. For example 10 years ago the best lightweight Li-Ion-powered cordless circular saw was only just a viable tool - the same size today in a brushless motor version is an automatic "go-to" tool, as are the equivalents in chain saws, reciprocating saws... and strimmers. But if you want a degree of battery future proofing it may be best to stick to garden tools from an established power tool manufacturer such as deWalt, Makita or Ryobi, etc - their battery connection technology is mature, long established and looks likely to continue into the future