Led when dealing with warrants, my way of thinking, in a nutshell, is this. 

Before expiry, I need to decide if the company remains viable. If I believe it is, I will exercise the warrants only if the exercise price is less than buying the actual shares at the time the warrants expire and write off the warrants.

My preference right now is RVX.WT.A with a longer time horizon.

IMO....Koo