This is a good safe idea, in a bear market if BTC climbs or dips even a little your alt value is most likely going to drop in sat value
In these conditions, I still invest in the coins I want and would hold long term, but at a 20% increase I sell, wait for it to dip back down then buy it again, been times where they've dipped after only 5-10%, I just keep holding in this case.
When the market is less bearish I hold my coins till I see a correction coming or starting then go back to BTC.
Been making nice profits even in this market with this approach.