...it just seems so slow....
Yes it is. But to expand on my earlier point, you should be very focused during this time despite riding along. There are plenty of things that can be worked whilst noodling around. Cadence drills, bike handling, positional work can all be undertaken during this time.
10 mile TT midweek if I am not racing at the weekend.
Highly recommended. If doing a mid-week TT make the day before an easy one and smash the TT - it will be a defacto testing session to check if training load is correct.
150W is like 45-50% of the OP's FTP - is there a great deal of value in a long recovery ride at that intensity? is there another way the time could be better spent? OP rides about a 10hr training week and we're talking about spending ~2hrs doing pretty empty kays.
perhaps a shorter recovery ride and some time walking, a massage, more sleep, etc, etc... idk, just asking the question of the resident experts.
The km are not "empty". Recovery rides are essential 1) to help reduce the training load for recovery 2) time to focus and expand on drills listed above 3) there are a few physiological benefits to low level training, not as much as high levels but with a race, hard group ride and FTP and anaerobic intervals the is no need for further work in these higher levels, indeed more work in the higher range could yield overtraining 4) a walk would be of no benefit here 5) massage is always good regardless of training load, the more the better 6) sufficient sleep should never be forsaken for riding time.