The hard part with a voluntary furlough is to get as much out of it as you can. Severance pay, Pass bennie's, insurance bennie's and in most cases you can file for unemployement. (depends on the state and how the company responds to the inquiry)
I would be hard pressed to take a voluntary furlough, unless I had either a sugar momma OR a solid job offer doing something I wouldn't mind doing for a few months to a year.
One last thing.. a plan from the company on how long you must be out and the process on getting back on board. Don't bite on something you could not handle and don't bite unless they make it easy to get back.
Yes.. your longevity stops right where you left it.. You leave at 3 years, 4 months and 5 days.. your first day back is starts at 3 years, 4 momths and 6 days.