Originally Posted by ill.clyde

Pretty much this ... but at 8 miles per day for your commute, I'd aim for 12-15 miles to stretch yourself a bit (assuming you've been commuting for a month or more?). See how that goes, and see how you feel the day after.

I don't stretch my rides every day. Generally speaking I'll stretch maybe one ride per week, or every other week, often dictated by my schedule, the weather, how I feel, etc. Even then, it only takes my day from a 24 mile day to around a 30 mile day. Might help to also vary the intensity of your ride if you're able to do so safely.

Today I pushed hard, nearly added 2mph to my average. Tonight, with that effort behind me and a temp of nearly 90 with insane humidity, as well as an expected side/head wind, I'll go easy. Tomorrow will be cooler, and if I feel like it, I'll extend that ride. Thursday I'll ride easy. Friday I'll probably drive to work and I'm hoping to do a long road ride Saturday morning.