So far, not concerned or planning on changing investment strategy. We're in our mid-30s now and our long-term financial plan is roughly something like so:
30s: Accumulate as much as possible (2 FT jobs, earning maximum $$ and adding lots of money to investments is top priority). Hopefully hit FI.
40s: Earn enough to cover annual expenses (so don't draw on investment/savings accounts, but don't worry about adding to them either, just reinvest dividends). Part of our thinking here is that it will be beneficial to maintain/develop some bankable skill sets just in case things do go haywire and we need to return to FT employment, and having a goal of covering annual expenses seems a good way to motivate ourselves, but removing the obligation to add to savings means we can be more flexible.
50s and onwards: REALLY retired--can draw on retirement accounts in a sensible manner. No obligation to earn money via work unless it's an interesting project that happens to also pay us.
So for us at least, if we are entering a bear market, it's going to have to be a looooooooong one to cause us serious trouble.
Also, I don't know what your current savings rate is, but if it's very high, might be worth reminding yourself that even if the market behaves in such a way as to prevent FULL retirement at your desired date, you can still be in a position to considerably cut back on your work hours, so it's not like you are stuck in your current situation for an extra 5-10 years. In our scenario, we will ideally be FI at 40, and the plan to not actually touch our savings/investments from 40-50 is just to add a little safety margin. However, our savings rate is well over 50% and we could easily cover all our basic expenses on just one income, so if we get to 40 and the market has behaved in such a way that we are not FI, we will probably still cut down to 1 FT or 2 PT incomes, enjoy the extra time, and hope the market resolves itself before we hit 50. If it doesn't resolve itself and we find we can't FIRE at 50, well...working PT from 40 to 55 or even 60 still sounds better than working FT until 45 or so just to hit the magic number.