Dr. Z.

As to what you were trying to do: If you have an existing IC like -2480, +2485, -2420, +2415 and want to collect more premium, you can just roll the short strikes, so you would typically buy back the 2480 and sell the 2475 (as a single order) and then buy back the 2420 and sell the 2425 (as another single order). Or you can sell the 2430 or 2435 or so, but this would make the put side wider and requires additional margin/BPR compared to the call side. At the end of that exercise you would still have a single IC, but it will have different short strikes than what you started with.

You effectively have ended up with a single 10 wide -2475, +2485 call spread. In theory you still have your 2 iron condors of course. But your trading software will probably no longer recognize them as such. Not the end of the world. In practice you will want to avoid doing buying and selling the same contract because it costs you unnecessary commissions and bid/ask spreads. If your account is under $25k it will also count as a "day-trade" (you're not supposed to do those with less than $25k)

Which effectively means that for straddles your "free trade" now starts to cost $2.50 per leg. That's not very attractive.

mukunda: IB has discounts for volume customers. See https://www.interactivebrokers.com/en/index.php?f=commission&p=options1 Unfortunately I don't quite do 10,000 contracts per month yet

Another benefit of IB is that option exercise/assignment is free, this saves you on option spreads and commissions when you have vertical spreads that went against you. Whenever you have to get out of those on TOS you get ripped off, especially when the options are deep in the money and have become illiquid.

Using IB, the average commission on the above was $0.68 per contract, or $2.72 round trip per calendar. I would have lost money if I had used TOS.