The short answer is yes, Vegas slots are open 24/7. However, there are some restrictions that may apply depending on the casino.
For example, some casinos may close their slots at 2am while others may keep them open until 5am.
The long answer is that there are a variety of ways to answer this question. In general, though, most casinos in Vegas will have at least one or two slots machines open at all times.
Additionally, many of the larger casinos have multiple floors of slots machines, so you’re never too far from a chance to try your luck.