I think we could not predict the future, so probably 30 BTC might not be enough.. It is better to have plenty...Bitcoin I think should not be our only retirement fund, there should always be other alternatives just in case bitcoin fails, but one thing is for sure, fiat would not fail, and other investments in real life like real estates...
If you have a plan to get retired only on bitcoins then its always better to have more coins in you wallet, as we don't know what value it will hold in future, either it will be higher or too low, so playing safe is the best thing we can do.