Lindsay Lohan in Rehab Until Further Notice

Lindsay Lohan will remain in rehab until her court appearance on October 22, and very possibly beyond that. Hey, when you're turning a profit, why not?
How long she stays in there is likely up to the judge.
The plan is for Lohan to stay in rehab until the hearing, at which point Judge Elden Fox will have reports from the doctors at the famed Betty Ford Clinic.
The judge will have an easier time evaluating Lohan's problems and progress then, and decide whether to keep her there, put her in jail or set her loose.
If the judge determines Lindsay would be better served in rehab than jail, where she's likely to be set free promptly, it's likely her stay will be extended.
As for the October 22 court appearance, Lindsay does not have to show in person, since in misdemeanor cases lawyers can appear on behalf of a client.
Judge Fox clearly remanded Lohan into custody last month, though, and expected her to remain behind bars until October 22. So she should be there.