LP. Now were talkin... You cant beat it for ease of use and clean burning...I don't have this problem because I'm running LP. Can't say enough about how convenient it is.
But I do firmly believe regardless of what fuel you are running, it is best practice to fire it up periodically to test function. It is no different than changing out the HVAC filters, just get into the habit because things go better because of it.
Our genny runs every Wens at 7pm for 15 mins w/ no load.