[SalesForce] Batch Apex gets stuck in Queued status for a long time

There are some tried and tested patterns for doing this, but if you'd like to save yourself some work and get extra functionality at the same time, you might want to check out Skoodat Relax. Skoodat have built a package up on the platform specifically for scheduling batches with as much power as possible and it sounds like a good match for your needs.

Otherwise, the limit of five jobs is being increased, and you can take the approach you've suggested. Depending on the exact details of the job you're running, you may be able to leverage triggers to do the processing on the other objects and just run the batch on your main record set.

In practice, Queued counts toward the limit of 5. We have added code to protect against the dreaded 'Attempted to schedule too many concurrent batch jobs in this org' LimitException (since you can't catch LimitExceptions)

Integer enqueuedJobs = [SELECT COUNT() FROM AsyncApexJob WHERE JobType='BatchApex' AND Status IN ('Processing','Preparing','Queued')] ;

if(enqueuedJobs >= 5){
    throw new TooManyBatchApexJobsException();
}

This article is confusing and contradictory too:

http://help.salesforce.com/apex/HTViewSolution?id=000182449&language=en_US

Relevant contradictory statements from that article:

• Batch Apex can have 5 concurrent (simultaneous) jobs running in parallel.
• That is, explicitly, the number of Batch Apex jobs whose status in the AsyncApexJob table are 'Processing' or 'Preparing'.
• A job is not executing when in Queued or any other status.
• Scheduling more than 5 Batch Apex jobs returns the error "Attempted to schedule too many concurrent batch jobs in this org"
• You may sometimes receive a Developer script exception e-mail when this limit is reached, but not always. (This is also by design).