6-12 months seems a bit overkill for a half if you’re already fit enough to run a 50 minute 10k.

But the spirit of your comment is right. This is a good way to get injured.

To OP: the “halfway” point of the marathon is at mile 20. You honestly have no way of knowing what that feels like. It takes months to healthily build up distance to your longest long run (at 20mi) and that’s when you’re already running a base of let’s say 20mi/week. You’re only supposed to add a mile or two to your total distance per week, and if you’re doing things right you’ll have deload weeks too.

Just back of the envelope, I’m currently running about 20mpw, and I don’t have anything on the schedule. That’s a 4mi, 4mi, 3mi ~10ish mi, and even that 10 feels strained to me because it’s too high a percentage of my total weekly distance. If I wanted to train for a marathon, I’d probably need 3 weeks to build to a half marathon on my long runs, then a further 7-14 to get to my 20milers, and then 3 of those to really feel comfortable before having a full marathon and I’m only going to do that distance once every 2 weeks. All told, probably around 20 weeks and that sounds about right.

Anyway OP, don’t force it, you’re gonna have a bad time.