misscrabtree456: 28 hrs, that's awful, and I bet you make all of 60k for the mission. I found the missions to be more than useless, just hassle that cost more than they are worth. Did 7 missions and that's it for me. Never want to repair a frigate again, or read some goofy message about how lame they are and couldn't complete the mission without getting ripped apart.
humbleman: The mission rewards scale with the length of the missions but so do the fuel requirements.
It's not unusual to get 2-3M is credits and 8-19 of each item that's discovered during the mission. OTOH, it's also not unusual for missions of 2000+ LY to require ~400-500 tons of fuel either. Bear in mind that ALL of my frigates are S class andf that's with 2x support class ships per mission.
Frankly, since I'm a day 1 player, and have long ago maxxed out on credits it's not worth the trouble of farming DiHydrogen for fuel to run the missions as I end up junking the vast majority of what I receive in rewards.
If you're just starting off or have started a new save they're probably very much worthwhile but I have noticed that the number of encounters per mission per LY, which is what advances your frigates class, have not increased at all so it's likely slower now to get a class C frigate to S class.
It's true that the more money and farming revenues you have, then all other activities quickly become a 'joke' in this game. I have still blueprints for farming and putting together items worth 15M, so once I have my base back it will be hard to convince me to go deeply in the Fleet thing, except for some time to know how it works out.
There is an advantage however in buying combat frigates: they do support you when you face more than 1 enemy in space, they will materialize near to your position and support you, but I haven't seen how many ships are launched and I didn't feel the 'power' of their support :)
My 300.000 credits per mission were all done with C-Class freighters + 1 B-Class. Also I may just have been very lucky at avoiding any repairs. At some point you may get a message 'We have run into trouble...We have to return'...Then you spend a lot of time landing on your frigates and doing the repairs which you have to do in 1 go, else the materials needed will change if you save and reload !