I am training for my first half marathon (in May) so take what I have to say in that spirit. I train 3x a week. Any more and I seriously hurt my leg and have the physio bills to prove it! LOL
I follow Jeff Galloway's plan, which includes run/walk/run and expect to have a 2:30 finish in my first half with NO injuries. That's the most important thing to me. Not the finish time (well, not as much! LOL) but how I feel at the end, and the next day.
I'm 50 and have only been running for 2 years, but that limits how much my body will tolerate with training until it starts to rebel! LOL
So with that in mind I train 3 days a week. Two 30 minute run days and one long run day. IF I did intervals, speedwork, etc, it would be on my two shorter days. I am actually going to join my local Goodlife gym so I can do BodyPump on my short run days. I plan on running to the gym, doing an hour of pumping iron, and then running home (for a total of 30 minutes). That way I can get my runs in on my strength days and that leaves me 48 hours of rest before the next strength/cardio session.
Galloway claims that 3x a week is all we need to train effectively. I'm taking him at his word, as his method seems to work for my needs and goals. I've been running injury free for over a year and a half now because of his method.
Might be worth a look for you too. You could do your shorter training speed work runs on your strength days and that leaves a few days a week where you can have a life too! (Also important to me with 3 kids and a hubby! LOL)