If you leave the vacuum pump running, then yes, you can evacuate for an extended period of time. If you are talking about pulling the vacuum, turning off the pump and sealing it off, that is NOT a good idea.

The reason is that if there is any leak no matter how small, you will be drawing in outside air, which always has at least a SMALL amount of mositure.

Since you've already done it and it held the vacuum well, then you have a LITTLE BIT of indication that there are no or minimal leaks. Evacuate again, before charging however.

If you don't have a micron gauge, it is very difficult to know if you have a leak with a manifold gauge. It's not NEARLY sensitive enough. Holding a vacuum even a few days with a manifold gauge will not tell you if you have a leak that would lose significant refrigerant in a month or two.

Hope this helps.

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