You can see that BETH trades in a pretty tight declining range, so I've been selling at the top of the range and buying at the bottom.
A few points to note:
1. Price is declining and converging, so it's getting harder and harder to pick the top and the bottom of the range, but it's currently well above trading fees
2. You obviously don't earn stake when you're back in ETH
3. You're going to get a trade very rarely
4. There's a chance that your sell is never hit, but since you're HODLing BETH you probably don't care
5. There's a chance that you sell and can never buy back at the price you sold, but I personally think as more people buy BETH and realise that they want to get out for whatever reason, prices will go down