Unless you're an big spending gambler, I don't think any of the mainline casino hotels downtown would like to have guests stay for much more than a week. They want to bust us in just a few days, and expect there's not likely to be much left for them to win after a couple weeks. That said, you can always ask.
I don't know if it's "decent" or not, but you might be interested in the apartment building that the group that runs the Gold Spike operates downtown, one block north of US95 on Las Vegas Blvd. It's called Siegel Suites Bonanza, and they offer weekly rates. Something to consider.
