For me, a general rule would be to never have more than $1,000 in a mobile wallet, and I don't think I've ever had more than $500 or so. The rest is in cold storage. I haven't ever had any problems, I haven't been hacked or anything, but just because it hasn't happened doesn't mean that mobile wallets are secure.
I don't have big amount in any wallet connected to the internet, I understand the risk which is why I don't store much money online, but just the amount I would want to use within a short period. I have seen the level of damage storing money in hot wallets can do, hence my resolve not to allow myself become a victim. Hardware wallets still remain the best but in the absence of that, other safety measures can be applied.
Yes, depending on the amount you have, you can go from one HW to two, stored in different locations, or multisig systems.