Yep those radial roller bearings get crud in them and fall apart
It will not be a catastrophic failure but the steering will just get heavy again
Having said that I have done the same conversion several times and it works well because after 2 to 3 years the steering gets heavy again so they call me back to service the mower
SO I get to do a full service every 2 to 3 years for the price of a $ 12 set of bearings which I do not charge for .
I also noticed he was using LMM grease which is not good for that purpose.
I use marine grease which stands up to the elements a lot better .
Even high tack farm grease would be better than LMM