FWIW, I think an 18 month support promise would be a reasonable first endeavor. The enterprise I worked at for several years did things on an annual cycle (as

FWIW, I think an 18 month support promise would be a reasonable first endeavor. The enterprise I worked at for several years did things on an annual cycle (as their customer interest was quite annual also). Project planning took this into account, so a year was a reasonable planning point - but things do slip, and having an extra few months with known support would be a relief factor.