I will like to know if Crytopcurrency mining is a worthy investment in the long term
Yes,
I bought almost all my rigs arround 2016 until now still mining.
or if it is just a waste of time.
Yes,
If mining use CPU and Mobile Phone.
since you are a veteran, I want to ask you how many times did you had to turn it off because of light price? l wonder if is normal this month is not profitable for me (mining since jun 2017) but it will be ok later on, or is a signal to drop it.