It totally depends on traffic and the route, and actual time.
I would hate a 30 minute commute if it was basically traffic the whole way, or stop start.etc.
45 mins, decent 60/70 mph travel, with just a little town drive at the end, would be fine.
I used to have a job from Northampton Area to MK, every day down the A5. So frustrating, I started at 08:30 and had to park in an ind, est. If I left at 07:00, I'd be late. If I left at 06:45, I'd get in for 08:00.
And it would be the same coming home, dependant on traffic I could get home at 19:00. So out the house for 12 hours, to work 8.5. When the same route at the weekend was 30 mins .
I took a 1.5k paycut for a different job where I could carshare with my partner, techincally came up on top, once I accounted for diesel.
My current job is a 22 mile commute, which is pure driving, takes me about 30 mins. Plus I have a couple of longer, alternative routes if my main route is full of traffic.
Luton to MK, you have the A5 and the M1, but they are very dependant on the other. If the M1 is bad the A5 is stuffed too...