It's such a hard one, isn't it? I've said before on this board that I'ver had a long term illness for many years, despite the prayers of many faithful Christians who have prayed for healing. My illness has shaped my life in many ways, most of which I cannot be conscious of as they are too intrinsic to who I am. It's stopped me doing things, but started me doing other things as well. It's been difficult to have dc, but I am really glad to have my two (no chance of any more after that due to illness). Anyone who has known me over the years will know the low points, the real pain and suffering.
Obviously, I don't know yet how my life will pan out, when I will die, whether I will get much worse, whether my later life will be absolutely awful with unbreable pain, or whether a cure will be discovered which will enable me to live a long and pain free life. My chances of a long life are lower than most people's, but hey, really, who knows?
So where's God in all this? To me, God is where God always is, whether we are well, terribly ill, or somewhere in between - God is in us, with us, in the breaking of bread in Holy Communion, in his body which is his people, on the cross, bearing our sufferings, and disguised as a gardener after the resurrection, calling our name and helping us to realise that He is alive. No, I know that's not much of an apologetic, not much of a rationalist argument for why someone with a long term illness still believes - but it is what it's like to be me, to see the world through eyes of faith.
...Which is another thing. I don't think any one of us has any right to question God's dealings with any other person. It'd be so easy for all of those Christians who've prayed for me to get all cross on my behalf because I'm still not cured, but, the thing is, they're not me. They don't know how this feels, how it affects my life day-to-day and long term. Maybe I don't yet, either. Maybe it'll only be when I'm old that I can look back and have some perspective on how illness shapes who we are. Maybe I'll never know, maybe it'll always be too subconscious, too intrinsically bound up wih who I am. Which is maybe why faith is the only way to live really IMO.
Sorry that was a bit rambling! But it's a big question.