I assume you're talking about weeks, not points. I can't speak about points. For a week's reservation, you can check in later than the check in date - but you need to let them know that you won't be there on the original date. You can leave early and check out with no problems. I also have left mid week and returned without informing anyone. But if you stay less than a week, don't expect to get any days credit or a cash refund.
Practically, if delayed in checking in, you should contact the the resort and inform them. Otherwise they may use an unoccupied unit to solve other problems. Smoke issues, maintenance issues etc. by switching units.
Not a problem in leaving early, some resorts will attempt to rent the extra days so checking out means checking out, I've often wondered what they would do if I reappeared. If you need to leave for a day or two mid stay it is best not to inform the resort to avoid any issues.
Rereading your question it is possible you are asking about something else and I have misinterpretered your question, if so, details would help.
Although you can't arrange it at the last minute, some timeshares (ie. Marriott Manor Club) permits you to split your 7 nights into 2 segments - a 3 night and a 4 night stay at different times of the year. I think there's probably a fee to do this.