Whenever I ask something in a post it seems invariably I learn something. Often it is something I hadn't even considered.

I usually fry fish in peanut oil. It seems to have a high heat tolerance and since I like to fry fish hot and fast it seems to work out. I am considering re-using left over oil on my next trip which is something I have never done. Probably a separate container and a small stainless steel screen to strain it of impurities. Good idea?

It would be nice to strain it while it was still hot but not crazy about the interaction of hot grease with a nalgene bottle. Suggestions?

Thanks PJ
I am intending a bit more lengthy trip than normal for next year and am evaluating every conceivable way to conserve weight and stretch supplies. I detest the thought of having to triple portage.

Scratch that one.

How long are you holding it for?

15 years restaurant experience here.  Cooking oil is reasonably stable & safe for this.  No restaurant dumps it's fryer oil daily.  Weekly is more likely.  Fryers are on for maybe 16 hours a day, 8 hours at room temp.

In many places oil gets moved down the line.  Take a 3 fryer situation.
-Fryer 1 is for items that don't burn the oil fast & need a good appearance - french fries.  
-Fryer 2 is for items that are battered.  Being the next dirtiest item for the oil.
-Fryer 3 is for items that are breaded or marinated.  Breading is murder for oil.
New oil goes in Fryer 1, Fryer 1 oil goes in Fryer 2 and so on until Fryer 3 is dumped and turned into bio-deisel or whatever they do with old fryer oil.
Fryer oil is filtered daily.  Unless you really crank the temp and burn the oil that way, if it's smoking it's burning, the big problem is little bits of food in the oil.

So I think you're fairly safe provided you follow some safe practices.

Never return used oil to fresh oil.  Have 2 containers.
Filter the used oil while it's hot.  It just filters/flows better.  A coffee filter or two will work.  Metal tools, 'cause the oil is hot.  I've seen people dump a whole fryer into a plastic bucket, the bucket melts and there's hot oil all over the floor. 
Maybe use a spare pot for filtering & then return the oil to a Used Oil nalgene once it has cooled down.
An aluminum foil wind screen, like what MSR stoves come with, can be re-formed to a nice funnel shape to support the coffee filter.

When re-using the oil, heat up the old oil first.  If you know what rancid oil smells like, it smells even more when hot.  FYI, this is also helpful when using stock or milk - heat it up and you'll know if it's still good.
Once you've determined the old oil is still good, top up with fresh oil.

well, if you demand deep-frying...that's one idea.  I've got used to just "frying" the fillet....a small bottle now lasts a whole trip, fish nightly.  No more submerging....just a 1/4" in the bottom of the pan, turn the heat down lower....and wait a few minutes longer...same great taste and minimal oil useage.  But IMO...if I demanded submergence of my fillets, or signifigant oil useage...I'd find bringing another bottle easier than the recycling hassle.

One trip, turned down the temp even further as no oil left, put some fake butter in the pan...low enough to not "burn" it....fish did get done and was indeed good.