At least once in the spring,usually 3 times a year.I fly out of an old grass strip 75x1400. I filled up an old 300-500 gallon fuel tank with 1.5 yards of concrete put chromolly pipe with spindles on the ends through center,tig welded frame out of 2x2 angle with a 2 inch ball coupler on end.Pull it with 4x4 truck.I have noticed that even a heavy rain will make it a little lumpy as the water moves through the grass.I keep the grass 2 inches or less.After it has been rolled you can tell a big difference just walking on it.It feels nice and flat with no lumps.I have been flying a boomerang off of it and the takeoffs and landings look like I am on asphalt,except for the fact that I slow down without the use of brakes.I have seen videos of jets taking off of grass and they seem to be getting bounced al over the place.Tha dosn't happen on my strip.I would think it is just a matter of time before something breaks.If you rolled it after the spring thaw I would think you could get by with a small roller from the farm store pulled behind a riding mower or ATV.It would sure be better than nothing.