If you invested in Sia two months ago for a long term... I'm really sorry but that was a fail.
As you can see in image above Sia was falling for really long time. That's not good info for Sia holders of course. In my opinion they deserved it (developers). There is already a lot better projects based on decentralized hosting so there is no need for another ones, really!
But let's wait a second. Why not to buy it right now? I actually did it and hope for some rising, HOWEVER, you should not follow as I'm amateur.