I am trying to reach my goal of a 4:10 for the 1500m this track season. To anyone who has previously trained in mid-distance, roughly how fast should my base runs be? I can currently run 5 or 6 miles miles comfortably at a pace slightly under 7min/mile, should I be pushing myself harder on non-workout days?
In short, no, you should not be pushing yourself hard (at all) on your non-workout days. You should ideally strive for an 80/20 balance, in that 80% of your miles are easy, and 20% are hard (i.e. sessions).
Your easy runs should be done at just that, an easy pace. A pace that you can talk to a running buddy, in full sentences, or recite poems or songs. The idea is that by taking the easy days really easy, you can then push the sessions hard and maximise them. It's a common issue with runners that they run too fast/hard on their easy days, and so do not go into the sessions in optimal condition.
However, without knowing what your training is like, in terms of key/example sessions with paces and overall mileage, it's hard to say how fast you should be running your base mileage. If you happen to train by heart rate, and know your maximum (which is not 220-age...) - then occupying 70-75% HRMax is a good guide for easy running.
Please feel free to add some of your training, and hopefully we can help to inform you a bit better!