Main thing is to have a proper slope on the discharge pipe. If it sags in the middle water can collect and freeze. Alternate solutions include heating the pipe or possibly insulating can help, or burying beneath the frost line.
I'm just a homeowner who had a frozen line last month and have read as much as I can. It doesn't appear that there is any such thing as "normal" for sump flow rates; every location has it's own characteristics.
A pump running every 10-20 minutes doesn't seem so bad though, compared to some that cycle every 1-5 minutes. Mine was going pretty often during the thaw last month but now it's silent. Every day lately the level has been going down 1/2 - 1 1/2 inches.