Upper limit?

I'm wondering if all identified ECMs have to be included in a longer term capital improvement plan OR if the audit revealed a project with, say, a 12 year pay back period and high implementation cost we could consider that to not be a viable project and totally exclude it from our capital plan. If not, should we just exclude these expensive/long pay back ECMs from the ASHRAE Level II report completely and only include those projects that we would consider funding long term that met some threshold of cost/payback that we could accept. Thanks!