If you have not experienced a downswing, its coming trust me. If you have, then you know that you can never have too much money in your roll to deal with downswings. That being said, intertops being on the lock network, and all other US sites have a certain percentage of risk of ruin due to unforeseeable or foreseeable circumstances.
Keep playing your bread and butter game ( low buy in rebuys and deepstack) and once you have a 30+ ROI with over thousands of game sample size, then start increasing stakes played. If you continue to play and increase stakes, you will catch a nasty downswing , and chunks if not all of your roll may be jeopardized. That being said , no one likes to grind micros forever, so another way to increase your roll would be to increase the number of games you play at once instead of increasing the buy in of your games. This will lead to more profits, and less variance, assuming you can handle the extra pressure of playing more tables at once.
If you were to ask a pro SNG player what to do with that roll , someone like BOKU
on stars would probably say something like , Id buy in to all the 1-5 dollar buy in MTT SNGS on stars and play untill I was busto or robusto. ( He can 50 table SNGS). My point is , the buy in should stay same but volume should be increased. This also helps in lowering the learning curve of MTTs by getting in more volume.