As others have said, if you're gonna be reaching that kind of timeout, the use case would come under this caveat I mentioned:
> assuming the task isn't hugely inappropriate
We have a couple of cases where reasonably small files (< 100MB but it'd work with larger) need to be downloaded from one place and placed in another, potentially with an ETag check to prevent redundant uploads/downloads. Lambda is perfect for that.
If you're downloading a file that takes anywhere near that long every hour then it's probably a bad choice for cost reasons too. Most files aren't big enough to take 15 minutes to download though.
If you're at the point where you're worried about the timeout, you should also be worried about the disk space available to your Lambda. The file should be stored in and served from S3.
