In my opinion, yes you can trust ethereum to hold it for long term like 5 or up to 10 years you just need to be patient for waiting because from what I've known in ethereum pricing, its price increased a lot from its past price imagine its presale price which is worth 30-40 cents per eth and now it is worth a 600 us dollars and it will be continuing to increased more by holding it for several years. You can use any wallet that is supported by ethereum.