I'm about 60% ETFs. QQQ and an S&P 500, split roughly in half by cost basis, and I don't rebalance just because one ran. The other 40% is single names. Most of them I keep on moomoo.
If a single name starts running on its own, I'll let the stock sleeve get a bit heavier. Then I point the monthly buys at the ETFs for a few months until the mix comes back. New cash still covers that. In a year or two it might not. That's a later problem.
I also cap single names. A new position doesn't start above 10% of net worth. If it runs I can live with 20%. GOOG I bought around 8% and it's about 16% now. Above 20% I start trimming.
How are you splitting ETFs and singles? If a name runs, do you cut it, or let it ride?