I typically ride at about 14 MPH. About 7 mile commute each way gives me a solid hour of exercise. I would describe my pace as steady and moderate. I don't treat it like a race, and I'm careful to look out for obstructions. I am quite satisfied with myself for just getting there and back by bike instead of driving. I'm big on efficiency. Maybe over time I'll get a little faster. I have had a bad habit of procrastinating, so I will ride harder when I leave at the last minute, but I am slowly getting better - my goal is to leave early enough to arrive 20 minutes early, but if I get there 10 minutes early I'm pretty happy with myself now. To keep things simple I try to leave an hour before the start of my shift regardless of conditions: ~ 30 min for the ride, 10-15 minutes to dress and walk to the shop, and the other 15-20 minutes in case of a breakdown or getting stopped by a train and for headwinds.

Headwinds obviosly slow me down, but unless it's extreme usually only a small bit.

My newer Swobo Dixon is a little faster than my older Mongoose rigid MTB, partially because I removed the front deraillieur and use only the middle chainring on the MTB.

Tailwinds save a slight amount of time.

Using the studded tires slows me down a surprisingly small amount.

Riding at night (my favorite) is a little slower because I slow down a bit to look at the road more carefully. If I ever have to buy a new headlight I'll get the next-brightest Dinotte - my 200L is adequate, but sometimes just barely. This is especially noticable on asphalt.