When is a Lead to Old to Work?

The reason I ask is two fold. I have telemarketed leads I bought that I never could reach. They are maybe 2 years old. I know they will not remember the call lol. So kinda curious if its a waste of time. They cost me $25 each and I bet I have 50. I also know Trans offers $2 leads that are mailers that were never sold Trans. Anybody ever bought these?

Thanks!

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