To call the moderation on Stack Exchange Chat inconsistent would be somewhat of an understatement. A flagged message might be handled by any of the 300+ moderators, the result is highly variable.
While there is a rather fuzzy line between acceptable and inacceptable behaviour in chat, in most cases it is reasonably clear whether a message should be removed. But there is a much greater uncertainty about what the appropriate suspension length is. Depending on who handles a flag, the result might be anything from the standard 30-60 minutes auto-suspension and a few weeks.
Unlike for suspensions on the main sites, there are no official guidelines from SE regarding suspension lengths in chat. This leads to wildly inconsistent moderator actions by different moderators for similar offenses.
An additional issue with this situation is that in my personal opinion the manual suspension lengths are often too short. They are usually measured in hours or a few days. Of course chat is a different medium than the main sites, but I think that even for a faster medium like chat a suspension length of a day or two is not all that useful.
The short (30-60 min) auto-suspension with a spam/offensive flag deals with immediate issues and lets the whole thing calm down a bit. That is enough for most situations. If that isn't enough, I would directly go to suspension lengths similar to the main sites, though a bit toned down. Something more like 3,7,30, ... days.
Manual suspensions are much rarer than the automated ones in chat, and usually deal with users that were repeatedly flagged or committed especially serious first offenses. The recent addition of annotations to chat users and recording of previous suspension now makes it possible to make chat moderation more consistent and to deal better with repeated low-level offenses.
Remember, suspensions are primarily a way to stop a problem from continuing. To the extent that punitive suspensions are used, they should be as long as possible; once you've given up on the idea that a user will come back and behave appropriately, there's no point in welcoming them back sooner than necessary - of course, that's a pretty good argument for avoiding punitive suspensions.
Ultimately, all suspension durations are left to the judgement of the moderator: situations vary greatly, and moderators should be free to choose whatever length of time is sufficient to allow the problem to subside. When in doubt, err on the side of suspending for more time rather than less; it is always possible to lift a suspension early if the matter can be resolved in less time than expected.
That out of the way, let's consider the various reasons to suspend someone in chat:
This includes dropping into a room dedicated to Android and interrupting the conversation about fragments with your relationship troubles, or interrupting the conversation about relationships with a link to your question and "URGENT!!!" by way of explanation.
These should usually be handled by kick-mute or the automatic flag-suspensions, but in extreme cases it may be necessary to give the frantically-confused author a few hours to a day away from chat.
Then there are the folks who make a habit of spamming every room they can find with their questions, inviting random people into rooms to see this spam, or simply drunkenly posting vulgar song lyrics everywhere.
These folks are much more likely to trigger automatic moderator-flags (triggered by multiple kicks) along with user-generated flags and kick-bans. The first time this happens, a few hours to a day should suffice; most people sober up and avoid these problems in the future. For those that don't learn, chat will cheerfully accept a 9999-hour suspension period.
This involves trolling, creating rooms to harass or hit on other users, and plain old persistently bad manners. Realistically, these should trigger a suspension on the main site: chat is not an isolated system, and if you're going well out of your way to abuse people there, then that reflects on your participation on main as well. The normal communication and escalation system for main-site suspensions should suffice here; in particular, the private moderator messaging system is ideal for situations where it is necessary to communicate the severity of the situation with a user after making sure their chat access is revoked.
It's worth noting that some people seem to be able to participate constructively - even admirably - on the main Q&A site, but routinely fall into abusive patterns when participating in chat. This is rare, but... In exceptional cases, it can be worth imposing a lengthy (or maximum) suspension in chat while leaving a shorter suspension in place on main.