Since I've been practicing on the defense side, the rule was that an attorney could not submit a voucher for payment on a case until that case was disposed of. Theoretically, an attorney could work on a case for well over a year and never get paid for it until it was over. Under that same theory, an attorney could have no money in his or her bank account, while the County owed him thousands of dollars in fees.
This made a bit more sense prior to vouchers becoming electronic. Previously, attorneys would have to handwrite out the case number, name, court, and manually write down all hours and court appearances. That voucher then got submitted to the Court for approval and then sent on to the Auditor's office (who would presumably enter the dates into a computer). Once entered into the system, the computer would check to make sure that an attorney had not double-billed or tried to claim payment for too many cases in a single day.
That was a pain in the butt, so it was understandable that the rule was that vouchers only were to be filed once the case was disposed of.
That being said, judges routinely allowed for interim vouchers to be filed upon request of the attorney. If a case was set for trial, but not for another several months, for example, every judge I ever spoke with had no problem at all with allowing me to file an interim voucher. All I had to do was ask.
But vouchers are now electronic, which makes life easier for all involved. Attorney seem to like it better. Conflicting time entries are caught instantaneously. Judges can approve them easily and ship them over to the Auditor's office electronically. It has drastically improved the efficiency and ease of keeping records straight, and it has probably saved a few trees in the process.
In the aftermath of Hurricane Harvey, trials are now routinely being pushed into 2018. Dockets are also staggered further out.
I would propose that attorneys be allowed to file interim vouchers whenever they need to, without having to first seek judicial approval. It is my understanding that those attorneys who take appointments on CPS cases get "paid as they go," and there is no reason that can't be the same for criminal defense attorneys. Electronic filing of vouchers should have eliminated any confusion or logistical argument against that.
If I'm working on a complicated murder case and I spend two weeks straight going over records and interviewing witnesses, it defies logic that I would have to wait months before being able to seek payment for work already done. I'm not familiar with any other industry that works that way. There is no real reason that indigent defense should be handled differently.