So the warrants expire in 2021 - late October (I think the prospectus was dated the 28th?).  In any event, no it is not necessary to excercise yet as there are 17 months to go and you could wait to 2021 and not pay the taxes due until April 2022 filing.  However, you are correct - the warrants do not trade and therefore liquidity could take a week or more.  So, if you want to hold something more liquid, it may be advantagous to switch to shares - particularly if you intend to take the gain in 2020 anyway. 

I am not really suggesting that all 34,000,000 are about to fly out at us, but i think it good to stay aware of my surroundings and understand what may be happening. Time has past and situations change, motivations of holders change. For example if the warrant holder is now deceased, the warrants sit in an estate account.  The trustees are unlikely to want to hold a speculative stock and so are likely to excercise with a view to selling the underlying shares...... this isn't likely to be anything other than a small minority cases, and excercising warrants does not mean the stock all comes out immediately - but it does increase the issued count.