I have not had any problems with a touchless wash. Some system use harsh detergents, but Zaino holds up well. I did a durability test on Zaino Z5 and ran my 330i through 10 times over a two week period with only a small amount of degradation of slickness and water beading.
Regarding hand washing with Z7, I think that depends on what you do after you run the car through the auto wash. If you dry and QD the car each time, I'd think you can go a month or more.
Don't get me wrong... hand washing is still best. However, I will be the first one to admit, time does not always permit.
db