Agreed I have been waiting to put new money into Bitcoin for the same balance reason. When I had to raise cash in January i did that with Ether, which turned out to be pretty lucky timing. In general I hate to sell because its an asset class that has a long way to go. Your idea is spot on to watch the currency pairs and rebalance on the tops. A simple way to help decide when to do this was shown by @pandorasbox by just doing a log trend of the pair and drawing the trend channel by linking the tops and bottoms. I included a snapshot below. I think it also puts your ratio comments in context.