I only have one FL lantern >15 years old. I have found the amount of light emitted is far less than an LED lantern, but is more directable due to it's design. The FL lantern I have will only work with full size "D" batteries, but lasts about 40 hours of use. I also have a 10 year old LED lantern that also requires four "D" cells, which I power up using NiMh "AA" cells with "D" to "AA" adapters, which works very well. I get about 30 hours of use using the NiMh cells. Both are single on and off functions. Other new LED lanterns offer different brightness levels which can be more useful with their extended run times. My FL lantern powered by "D" batteries, which were/are stored outside the lantern until needed for use. Alkaline batteries always have potential of leakage, and I do not risk having to acquire a replacement lantern when it is needed at times when a replacement is not feasible or possible.
I would not get rid of the propane gas mantle lantern. They work the best, IMO, when needed camping, and times of need. Most have an adjustable output. I do not know much about current LED lantern offerings, they may have surpassed the tried and true gas mantel lanterns that have worked awesome through the decades I've used them. Just make sure You have a spare gas mantle on hand for the gas lantern when using it, as they are fragile and do tend to wear out through lighting and use. Much like having spare cells for an LED or FL lantern. I too prefer a tail standing LED flashlight indoors, but have used gas mantled lanterns indoors without any negative anomalies. I also have and still use lamp oil lanterns in times of power outages.
I would vote to sell the FL lanterns and replace with LED. The FL tubes in the lantern do burn out over time and are becoming harder to acquire and replace as technology advances, IMO. My FL lantern still has it's original tubes, and has only been used lightly working on and beneath vehicles. I have not needed it in years due to the cordless power tool lights of present day.
Take Care
GL