Feeling up hot sister..
I used to go into my hot older sister's bedroom at night, every night, and feel her body like crazy. Would go inside her robe (if she wore one), start with her bulging tits, move down her body and flat, sexy midsection, and plunge into her thong undies (same thing..if she wore any), palm and finger her, then go around to her perfect ass. Did it so often had it down to a science.
If she fell asleep with her door locked, I had a steel nail to undo the lock hidden on top of the door trim, and would quietly unlock the door. Having the tv left on only made it easier for me, as I didn't need to be as quiet.
After awhile, she figured it out and, running errands with her one weekend, told me I could keep going, she wasn't telling me to stop (she enjoyed the attention), but..if anyone saw or found out, she wouldn't defend me. It was all basically my thing and call.
To be honest if you think shes hot, and shes fine with it, keep getting your pleasure just stop when you're told to.
OP, just found this post again. In response to your statement, we both enjoyed it, and she let it go on as much as I wanted to keep feeling her up, which was pretty much every night. I did hold up for a little bit, not so much at her telling me to, as her reminding me that someone else in the house had a late schedule, and was often home and awake when I was going into her room and having at her body. She was really advising me to be careful and not get caught. I held off for maybe a few weeks, to figure out the hours, then started going back in and having my fun.