Is $700 to replace dryer vent a fair price?

I currently have a dryer vent installed with a flexihose that runs from the laundry room to the ceiling (5-6 feet) and then through the attic to the outside (15 feet), totaling about 20-21 feet. It appears to be two hoses attached. I've been using my dryer for 12 years with this setup without any issues. However, I'm concerned it's a fire hazard because online sources and the Class 1 air connector specification state that flexihose is not suitable for dryer vents. I've called many places, and some suggest leaving it as nothing has happened, while others refuse to clean or replace it due to the material and potential for tears. I'm debating whether to keep the same route (22 feet or longer) or reroute it for a shorter path to ease the dryer's fan pressure. I've decided to get it changed and am also wondering if the transition duct length is included in the total duct length.