I've bought a few OEM EVTM's and have found for the most part those are compatible across a few years either way. There will be "division years" where things change somewhat dramatically where they might not be usable. Going from '96- '97 would be one instance. Another might be when RSC was added (not sure when that was first offered.)
Most chassis past '09 should be very similar so your year spread would be worth the investment.
If you're not in a huge hurry I'd create an eBay search with notifications for your specific year, jump on the first good deal if its in the budget. Get the printed versions only because CD-ROM OEM manuals have expiration dates which makes using them a bit of a hassle. (Someone will know how to "cheat" that embedded coding but its not me.