More important than the material is being sure the line has no low place(s) where water stands. That would be difficult with any flexible material. It sounds like your system is draining through the emergency drain. By code in most locations,the condensate is supposed to drain into the sewer. When the primary becomes clogged,the emergency drain line is intentionaly located to drip in a conspicous place. My favorite location for the emergency in rental property is above the shower so tenant notifies landlord quickly.
So with all that said,I suggest increasing line to 3/4" pvc and checking into primary and secoundary drains.

Thanks for the input klem1. The drain from the evaporator pan does have an overflow and it is also a 1/2" garden hose that is routed out to the eave and through the soffit, neither the main drain nor the overflow have ever been routed to a sewer. No codes out here in rural southern Illinois! Only once in 25 years has the overflow kicked in becuse the main hoses had a blockage which was easily corrected by running a thin snake through the hose.

My main concern is the longevity of the hose, which is just a run of the mill garden hose.

I'm in suburban Chicago with AC system in the attic of my 1 story home (hot water heat). The evaporator has a PVC pipe which drains into the nearby bathroom vent stack. Suspended under the evaporator is a drip pan. It does not have an emergency overflow but has a small mercury float switch which cuts off the thermostat lead if the float goes up.