How about a task you'll perform twice.
First go and get one of your flatmate's shoes.
Time yourself as you edge three times.
You must be naked, somewhere in your flat other than your bedroom and you need to be sniffing and licking the shoe as you edge. After the first edge spank your pussy 10 times, your ass 10 times and twist each nipple 10 times.
After the second do them 20 times and 30 times after the third.
Now if you want to orgasm you have to do the task again with the other shoe from the pair, but you must wait.
Take the time you took to do the task the first time and add a third (so if it took 15 minutes, you add another 5 minutes for 20 in total). You'll do the task somewhere else in the flat, but again not in your bedroom.
You must start the task a second time no earlier than this amount of time before your flatmate is due back. If you manage the task before he returns you may cum. But you to do it whilst continuing to sniff his shoe and may not return to your bedroom. If you have to stop so or move somewhere else so you don't get caught, then sorry, but no O
