It's such a subjective question mate, as everyone has different reasons for running, and will also enjoy different things about running.
Personally, I don't enjoy a run to its full merit, unless it's more than 8-10k.
Cant put my finger on why, other than enjoying the feeling of fully switching off, and just being out in the fresh air for longer.
My advice, would be to try some longer runs and perhaps aim for a canal, or towards greenery.
I do mix up my running but I don't play to a schedule. Normally aim for 3 or 4 runs a week; a 5k, 7 or 8k, 10-12k and then something 14+k.
I think i saw you reply to someone else saying that you don't particularly enjoy running, which I guess may be a tough one, but could be that you're like me and would prefer running slightly longer distances? Got to be worth a try mate.