The offline wallet is always preferred when you have big or small investment and with he portfolio. In the long terms your portfolio will grow in the price and the value into your wallet will increase automatically. This can be seen with ether address or token address and it could attract the potential hackers. This is simple fact that they will take lot of efforts if your wallet contains worth amount of wealth really. So the good idea is to hold it into offline wallet and if possible and you have big investment then just switch to hardware wallets like ledger nano etc. But never keep the funds in the online wallet in general. You may sometimes loose the private keys, or keystone files etc. This cases have already been registered many times and people have offered thousands of dollars to crack the wallets for getting back their investment. So do avoid that trouble you must use offline wallets. The easy one.