>Running 101>Ran 4 miles, instead of 3, when to try 5?
at this point I would suggest running by duration also, don't worry about pace. nice & easy & build up time on feet & don't worry about intervals. build a bigger base ( more miles/duration). the bigger the base of the pyramid the more it will support other types of faster paced w/o's in the future. and the biggest help would be to add another day or two each week even if they are only 2 miles or so. after a few weeks of this (progressing up to 15-20 miles/wk consistently) you could just start throwing in a few short sprints into your runs 1-2 times per week or pick up your pace last 2-3 minutes. simple as that, don't overthink or add extra stress too fast.
Running easy (not breathing hard) is good.
Running every day, or at least more than twice a week, is good.
Running farther is good.
Your body will tell you if you went too far. If so, don't go as far the next time.
Save the fast running for a race.
I ran four marathons without doing any fast running. My best time was 3:51. Then I added weekly tempo runs and got my best time down to 3:49.
Fast runs? I would hazard a guess that not even a single runner I know would benefit from speed work of any kind. Why? Because virtually every runner I know is nowhere near fast enough to be considered an elite runner in their respective age groups.
As for improving times, I've done nothing but lots of long distance running this year, and yet my "Fifties PR" for the 5K has been improved from 25:20 to 23:39. Funny thing though, two and a half months after I ran the 23:39 5K, I ran a 48:24 10K on a really slippery course (meaning I believe I would have been significantly faster had the course been dry) which, per the Runner's World "Race Times Predictor" would equate to a 23:13 5K.
Long story short, I personally don't see any benefit to doing speed work until one is knocking on the door of the elite runners in one's age group.