Most heatpumps are titanium exchangers, those exchangers will outlast most other parts in the heatpump -stagnant saltwater or not. Your compressor will kill the machine long before the exchanger leaks.
That being said, if it's easy for you to install the bypass and you can drain (winterize) the heatpump for half the season, there's not much to lose by making the full bypass.
If you have the parts, I'd say do it.
Will
The Pool Company
Toronto