Sean - depends what you're training for I suppose and what the purpose of the runs are. If you're looking at running twice on days where you're doing a session, I'd have said the second run should be pretty short and easy, no more than 4-5 miles. On other days, I'd have thought there's something to be said from having one of the runs longer for the aerobic benefits, so for instance one run of 8 and one run of 5. In marathon training, some people use 10 + 10 as a key training day, but I guess on the basis of your age that you're probably looking at shorter distances.
Personally, I tend to run 4-6 + 4-6 on non-session days, but that's just because I'm running to work and back.
But also agree that if you're taking it seriously enough to be running 85 mpw at 17, you're probably better off getting some formal coaching rather than listening to the likes of me.
In answer to your question, when this thread started in 2010, I had a load of PBs from when I was 16/17 that I mainly couldn't remember but included my half marathon PB of 1:29:45 from probably my last race before 14 years of inactivity.
In 2010 I had just finally managed to return to being a regular once a week jogger. After a year or two of running once a week, I entered some races in 2011, and ended up with a 1:33 and 1:35 half marathon, and broke 40 in the 10K. This made me think I actually had something I could work on, so I decided to increase my training, initially to 4x a week, but then ramped it up soon afterwards, probably too quickly, and joined a club. Early in 2012, I also joined this thread, and much of how I structured my training was based around what I picked up here.
For quite a long time my weeks were regular 1 x tempo, 1 x intervals, 1 x long run, everything else easy, all year round. Broke 35 for 10K in May 2012, and was down to a 1:16 half and 2:50 marathon by the end of the year, and 2:40, sub 1:15 and sub 34 during 2013.
In 2014, after a largely failed marathon campaign, I started to try to preiodise a bit more, rather than having a similarly structured week all year round. Off the back of the base miles from the marathon campaign, I used increasing length reps of target 5K pace to break 16 in July 2014, and used a similar approach with 10K pace to get under 33 in November. Then ditched speedwork to use long MP tempos and shorter HMP tempos to run 71:38 at Wokingham a few weeks ago.
I'm fairly certain that specific, periodised training tailored at specific distances is now the only way I will continue to PB. The days of 1 x tempo, 1 x intervals, 1 x long run per week, every week, are probably gone for as long as I'm shooting for PBs.
But it's still a real experiment, and I'm only 3.5 years into proper training, so who knows how I'll decide to mix it up.
I don't get coached - our coaches set track sessions but, with specificity now being key for me, I mainly do my own thing these days - and I find running books hard going, so what I pick up on here, as well as the Sub 3 thread, is the single biggest factor influencing how I train. So, I do think collectively any successes I have are partly due to the influence and support of people on here - if that doesn't sound too much like the ending of a shite sports movie, possibly starring Kevin Costner.
Fifth birthday parties are the worst. The kids have just started school, so don't have a fixed group of friends, so you end up inviting the whole class. So you go to 20+ of these bloody parties in a year.
For those who haven't got there yet, take my advice and book a kid's entertainer. A good one is well worth the cost. For our oldest, we thought we could manage with just us, but it was a struggle even with the help of my mum, who was a primary headteacher. Of course, I didn't help matters by turning up halfway through dressed as Batman. I naively believed the children would keep an awestruck respectful distance, but instead they swarmed all over me like ants on a jam sandwich. Mind you, you should have seen the fear in my son's eyes when I had to give him a talking to, still dressed as Batman. He didn't know what to think.