I withdraw $1500 whenever my balance in PayPal hits $2000. I pay one of my major business expenses through PayPal, while not all sales come in by PayPal, so I end up withdrawing 1-2 times a month.
There's no super scary reason to not leave money in the account. The absolute worst case scenario would be your account being closed or frozen, which is not a normal situation. If that were to happen, your funds would be held for 6 months in order to be available for any disputes or chargebacks filed against the account, after which you can withdraw it.