“sometimes customers say they will join if you build a particular feature if possible make them commit by paying for multi-month subscription with the guarantee that you built the feature within a reasonable time frame otherwise them telling you that they will sign up if you build this that's just an empty promise”

Force "I'll sign up if you build X" prospects to pre-commit with a multi-month plan

"Build X and I'll sign up" is one of the most expensive lies in early product development — you build the feature, they don't convert, and you're stuck maintaining bloat for one phantom prospect. Convert the conversation: "I'll build X if you prepay 6 months at full price, refundable if I don't ship by date Y." Real prospects pre-commit; tire-kickers go quiet. Either way you stop building features for non-customers.