Advice for a Th9

Okay,so my current condition is:
Heroes both LVL15
Walls LVL9
All defenses maxed
Troops almost closed to max, im just left with valks,healers and gobs.

Okay so my question is:
If my upgrade my heroes one by one back to back,it would take me 30weeks to max them,which is like more than half a year,but if i were to upgrade both of them together, it makes it more troublesome to snipe THs. So which do you think i should go with? One by one or both together?
And should I max them before going to TH10?
And also my walls,should i get them all to Lava? Well i think i can get them to lava by the time both heroes are maxed by either ways.

its appears you have already decided not to move on to th 10. which I agree with

work on your heros as you get the dark elixir and seeing that you are going to take the time to upgrade them and you feel that you will be able to upgrade your walls to level 10 why not upgrade them, other wise your elixir will just draw un needed attention to your base

Easy answer. If you like war and care about it a little bit, you max your heroes.

If you just farm then do whatever the f you want and consider fun

off-topic but I would max your healers. super queen wrecks pretty much any 9's DE storage

One by one, and when you know you wouldn't be able to play Clash for a little while, then upgrade both together. TH9 is the most enjoyable town hall. Enjoy it while you can.

You should definitely go for level 10 walls, and do you heroes one by one till at least level 20+. After that you should try it by 5's, that's what I did I got my queen to level 25 first and then started my king I found a bit better, but that's just me.

You might as well do bot at once and don't worry yoo much about lavas but i would get as many as you can done before heros are finished. I also don't think th 9 needs to max heros. level 20+ heros should be good enough but level 30 might save you some time.

I would say alternate your heroes, especially if you are pushing or warring. However, if you are doing neither atm, then do both at same time. And of course, just keep chucking away at those lavas and however much you do of those while doing heroes to 25 is bonus. Then head on up to th 10!