You don't 'lose' anything, you gain a second set of creds that have an independent lifecycle. The only time this is awkward is if you're using the web console b/c you need to keep going through the assume role/return links.
That's what I meant, but admittedly I communicated it poorly - you need to reconfigure various bits of the code to use this credentials chain, which can sometimes not be supported by poorly written tools.
Not to mention you can just use a new --profile for that session and switch between them with a single argument or environment variable. I don't think it's possible to get easier than that :)