It depends how early you joined, how many people there are now, how many there will be soon, how much equity founders still have and how valuable they perceive your contributions to be (past, present and future)... consider that they both need to have the equity to give away and a material reason to part with it, not just because someone desires more. It maybe time to get moving if you have a bigger risk appetite and if they're not providing growth oppys or increased responsibilities... because often people outgrow companies and vice-versa, and that's okay... Never stand still.