You should still be honest with employees. They'll prove better in the long run if you are. Not a lot of stories where withholding the truth from your employees ends up being something that a boss feels great about...
It would generally be advisable to tell someone coming in "We have 2 months of finances, but expect (or need) to close this large deal to get some sustainability." But at what point do you not need to have that conversation? With 6 months of money? 12? 24?