i have 5, the 4 boys aged 11, 9, 6 and 3 and an 8mth old baby girl!
i cope and enjoy it most of the time 
i have to be organised ie when school is on we have to be out the house by 8:10am so its up by 6:30am for me, shower and dressed, then kids up and bfasted and deal with feeding baby etc whilst boys get themselves dressed and i tend to just chuck the bfast pots in the sink for when i get back...
the kids do help, ie they keep their rooms tidy, they put laundry in the basket or the washing machine, they will load and unload the washing machine, clear the table, elder two will sometimes wash up, they LIKE to do stuff like sweep the floor and hoover..
you just get on with it i guess? i always wanted four, then once we had no 4 we thought one more would be fine and it has been, the boys dote on her and are very good at playing with her etc.
i have them all in bed by 8ish, 7:30 on school nights tho the elder two read for a bit in bed. and then i have a made half hour tidying, washing up, sorting pack ups, uniforms, pe kits, swim kits, bottles etc etc before i collapse on the sofa and watch crappy tv.
when at home my dp helps, but he works crazy hours, currenlty been away since last friday lunchtime, he gets home tonight!! YAY