How many times can I reuse deep frying oil?

I got a Waring Pro 1800 watt deep fryer and love it. I’ve used it 5 times and have only used Canola oil. I let it cool and then strain it through cheese cloth. I then store it in a cabinet at room temperature in the plastic gallon container it came in. Below is each time I’ve used it and what item(s) cooked:
[/li][li]Onion Rings
[/li][li]Yams, Zuchini, Mushrooms + Scallops and Shrimp
Since I cooked fish last I was planning on only using it for that now but wondered how much longer it should be used now. So who can tell me what should adhere to:
[li]Is there a flash point or something that I should adhere to?
[/li][li]A color?
[/li][li]Times used?
[/li][li]What cooked?
[/li][li]Maybe there’s a chart or something somewhere?
[/li][/LIST]I want to try making donuts next and want to buy the oil for that and more Canola for a base, I guess. So, any advice is appreciated on a good basic oil and what bakers use with shopping at Costco in mind.

Use it max 3 times. If it’s possible change it after every frying.

Dear KW,

This is my problem too.

After every frying I wonder what should I do with the spared oil .

When frying we need lot oil to fully deep the pieces in the oil for perfect frying.

But it is really a matter of thinking with the spare oil . We cant easily throw It in the dustbin as it is also a question of cost .