Anyone have any wisdom on how long a 5" unit can run on a sealed lead acid battery? Is lithium worth the money?

It can probably run 24/7 for 3 weeks - assuming you get a Group 31 AGM battery. You can get a good one at Sam's Club for less than $200 out the door, but they weigh 60 pounds. You might want to propose WHAT battery in your question. With the proper specs for a particular battery, it's possible to calculate a ballpark run time.

Personally, I think lithium is worth it when you are powering a larger unit. Lithium batteries are smaller, lighter and last a long time.

How long can you run depends upon the size of the battery. Lowrance website says that a 5" Hook Reveal pulls .9amp with full backlight.

So, a 10amp hour Dakota lithium (about $99) will run it for for about 11 hours. An 18amp hour Dakota (about $175) will run it for about 20 hours.

I have never owned a Dakota... But folks speak highly of them.

I run a small lithium that weighs less than a Coke and after a 9 hr day my Hook Reveal 9 with Triple Shot ducer gets it down to about half.

What lithium battery do you have? How long have you had it? The dakota Mike speaks of above was really the only one i was seeing. But after you get that, plus the specific charger for it, you are in probably 150...

I run the Nocqua Lithiums. I have one going to my Lowrance and the other wired for the LED lights. I have had them for just short of a year now. They come with chargers.

I ran this unit on a 7 ah LA battery and it lasted all day. I never tested to see if it would run longer. Here's a lithium battery that will last you all day on the water at a great price. This battery runs my live well (which is 3 times the amp rate than your FF is) for 4 hours continuous. I charge it with a regular 12 volt car battery charger (on the 2 am setting).

https://smile.amazon.com/gp/product/B07Q7FY8CC/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

I bought an FPV 17ah and I love it. I have a 5” Hook2 and I’ve fished for 18 hours over three days and it didn’t run out of juice. Weighs two pounds and is sealed so you don’t need a waterproof case for it like people use for deer feeder batteries. I bought some Velcro and it stays put in my kayak.