I'm trying to figure out the max possible number of private keys into electron to claim BCC.
I dumped 3 old qt wallets (yes, I know that's an absurd number of addresses) with a fair amount of dust and imported them and have had electron stuck synching for 4 days now. Restarting it seems to kick it briefly but then it freezes again. To be fair some of those wallets are very old with a fairly long history.
I also tried on another box with just the keys from a single wallet and the process is identical
In both cases, I am connected to 10 nodes.
You're probably better off trying it with say 20 private keys just to check there isn't an issue with the server on electrum.
Then take batches of 20-100 private keys until all all your coins have been redeemed.
In your network settings you could try changing the node you're connecting to also and switch to have it connect to a different peer as it can only connect to one at a time.
You might be able to sweep the keys instead which might speed it up but will cost you in transaction fees.