The risk of you forgetting a pass phrase, losing a piece paper or having a USB die is probably higher than you getting hacked.

Personally I'd go for an encrypted copy of a key on USBs or paper in at least two locations.

If you have a significant amount then you need to think about the risk of you getting hit by a bus. For this a 5 part key where 3 out of the 5 will produce the main key could work well. Maybe keep 2 at home, 2 with your next of kin and one with a solicitor or bank manager?