If your insurance covers it anyways and you feel you want to do it anyways, go for it as soon as you want to. If the issues with the face ar ein the bones, no hormones will change that. If your issues are however others, you may want to wait, but since you are informed about FFS and have done insurance work already, I am sure you know enough about FFS to know which things will benefit you in any case.
It is a major surgery though, if you are willing to take the risks and consequences - that is more the thing you have to decide. Honestly, if I would get it paid for and not fear the risks and negative outcomes, I would go for it. Even at younger age. I was in my early 20ies when I transitioned. I did not need it back then, but I still did not like my face and if I had the option , I might have considered it. Hormones do a good job at that age and I looked good for years, with age it kind of starts to diminish a bit and previous features resurface slowly. So it makes little sense to wait. I think what you really should think about however are the risks and consequences. There are surgery risks, there is the risk of an unfavourable outcome that looks like something was done and there is the risk of some damage, like nerver damage, scars, damage to frontal bones or sinuses, etc. These risks are what keeps me from doing it presently even though I would have the money for it. If those are not worrying you, I would go and find a good surgeon and start up 😉