Best insight is to collect all your goods in a timely manner. First off, have 1 or 2 times each day that you can basically commit a couple minutes to, for collection purposes and then set up your various buildings to produce at those designated times.
Main reason you probably have a regular sniper (besides the bad luck of him/her not disappearing during a neighborhood change) is because you have some juicy buildings that he/she can collect from all the time.
If you leave buildings unattended for an extended period of time, than you can expect that sniper to continue to enjoy their game at your expense, as well as him/her telling a couple other people in the neighborhood too that there is a good city for the target on a regular basis.
At the end of the day, decide what is more important to you (a) playing a game with some possibly minor setbacks or (b) stopping someone else from enjoying their game at your expense.