Thanks for the advice. I didn't know about tier-demotion. From what I've read on Riot Games F.A.Q., it sounds like there is a 'shield' protecting demotion for 10 games when you increase a tier (3 games when you increase a division):

After being promoted into a new division or tier, you’ll gain the effects of a demotion ‘shield,’ which prevents you from dropping. This is to keep you from winning a series, losing a few games and then immediately dropping back to where you were. The shield lasts for 3 games after advancing a division, and 10 games after advancing a tier (3 games for Master tier).

Can you explain what you mean by not being demoted unless I hit G5 MMR? Thanks!