I could only consider it useful, for airfields in which you cannnot spawn, but use as frontline fields for refuelling and rearming - no repair. (Provided the right vehicles are around - as in DCS BlackShark). There I would consider 15-20minutes as realistic. This will still be better than flying 30mins back to your base and I usually have 1hour to 1,5hours flight time if I go for realistic missions, so I usually do only one sortie an evening.
For the usuall take-off, shoot, die, repeat - fun, I don´t see the point in landing anyway?
