I somehow lost a savegame, so I had to replay seelion from the start. Dont know if I was smarter this time, or if your update from 14.12. already changed something with the respawn of planes. But Dover and Brighton was a way easier this time, but not easy at all.
Dover is ok so far. I killed 7 hangers and it has effect on the enemy repawn. I could handle it. The hangars are not protected by bunkers, so can kill them all.
Brighton. Like I said at the beginning this time it had the feeling, that the repawn is less annoying. But I also used some nasty hero combinations this time. Camo + double support, so my 2 AA guns were shooting all the time taking out 3-6 planes all the time. But still, they are running out of ammunitions and cant protect everything. My fighter got some double attack + overstrength + no retaliation, so I could take out 4-6 enemies every turn. And thank god the AI is stupid, attacking my level bombers all the time, while my fighter do support fire. So the AI ruins like 4-8 fighters in some turns. Problem is I was running out of stock of level bombers. Submarines did a good job to kill the enemy navy. Since this stupid AA mod of the ships is so annoying, sometimes you cant even attack by air.
I kille 7 hangards, some of them are hard to reach, so you have a constant respawn.It is doable if you have a hard focus on air and anti-air.
Epsom. Just a pain in the ass. I killed 11 hangards in the end, some are unreachable under normal conditions. There are plenty of planes spawning all the time and you cant really get rid of them. Even with using some unfair tactics like I said above you cant protect your whole army. So you are taking losses all the time, which makes the map really hard and frustrating. Plus the reinforcement the british get anyways in this map.
Imo just too many planes or too high rate of respawn. 
Portsmouth. Its ok again, but still annoying most of the time. I noticed the navy is also respawning als long as the carrier is alive?!
My problem was I almost had no JU-88 left, so I had problems to kill the navy. I once again took out 7 hangers, one survived.
I tried to comprehend how much planes are spawning depending on the numbers of hangars but thats not really possible, without using the cheatcode to lift the fog of war. This time I felt some effect after killing the hangers, which is good. But still the overall repawn is too fast. The game feels like 80% is dealing only with air and anti air, which is too much imo.
And I did some statistics this time 

It took 29 airfields this time. I was 13x rewarded, 16 not. 
I got:
- 1x Spitfire MK II (nice!)
- 6x Spiter MK I (garbage)
- 1x Hurricane MK I (garbarge)
- 2x Battle MK II (huge garbage)
- 1x Wellington MK IC (ok...)
- 1x Beautifigther MK I F (nice!)
- 2x Blenheim MK I (garbage)
- 1x Whitley MK V (ok...)
After 4 missions vs the british I got a lot of barage. There is no reason to use anything of that.
I got some additional Spitfire MK II and I can run 1x Beautifighters, as long as the take some damage.
For me the feature doesnt do anything. I prefer to sometimes find some caches. 
In the russian campaign I dont see a reason for this feature at all. Even the best russian stuff is garbage.