There are a few things you can consider:
-
Hash rate - this shows the amount of computing power that is dedicated to mining. It's relevant because it means that people have enough confidence to invest in BTC's long term future. A declining hash rate would be very bearish, especially as ASICs constantly get better and cheaper. You can see hash rate
here.
-
Scaling - this is an ongoing debate about how to make Bitcoin capable of handling more transactions. I regard any scaling solution to be bullish in the long term, but
chain splits can be bearish in the long term. You can see which solutions miners are supporting
here.
-
Supply - a limited supply which would be extremely difficult to change (like Bitcoin's) is a good thing. You should check the planned increase of supply each year. Keep in mind that every 210,000 blocks (approximately four years), the increase in Bitcoin's supply will be cut in half. You can see the current supply
here.
-
Transactions - this is about how much people use the Bitcoin network for transactions. In the long-term this number has risen, which is a good sign for BTC adoption. You can read the amount of transactions in the last 24 hours
here.