It is safe to use as many wallets you want but the question arises how you use those wallets as many people complain of getting their bitcoin wallets hacked because of some virus or installing a hidden malware into their pc due to which their bitcoins got stolen. So you must keep your bitcoin wallet protected by a password and have an antivirus software installed onto your computer and also have firewall installed and up to date as there are security flaws discovered every week or so.