Brian I think we see more reports of air bags being replaced on older Motor Trike conversions for that exact reason. Simply, they have been around many years.
My previous trike was a '06 GL1800 with '10 Motor Trike Adventure conversion. When I sold it and bought my 2015 that conversion had nearly 50,000 miles on it with absolutely no air bag problems. In short, I do not believe there is any trend.
If you find a Motor Trike IRS you like don't let the air bag keep you from buying.