#1 Yes. You are likely to get a speed that is not what you finally intended. It also forces the old fragile gearing. I have read and follow the procedure of setting the speed, cocking, firing the shutter to make sure it is working at that speed, composing, focusing, cocking and firing.
#2 probably. The potential is to forget to reopen and fire the shutter. If you leave it too long (a month or two) the shutter will freeze and you will be paying $80-$120 for a cla (clean lube and adjust.) Painfully, I have done that with large format. It is a waste of time and money, but it makes the lens more valuable when you sell it if the cla is recent.