Como dizer "desculpa por ter te segurado esse tempo todo" em inglês

Olá BlackShot,

Se você quer dizer no sentido da pessoa estar esperando por você por muito tempo, usa-se bastante as expressões:
1. "I am sorry to have kept you waiting", se a pessoa estava te esperando e agora a espera terminou; ou
2. "I am sorry to keep you waiting", se a pessoa estava te esperando, mas ainda vai precisar esperar mais um pouco.

Espero ter ajudado!

Abraços,
Renata

Sorry for taking so much of your time.
Sorry for taking so long.

In slightly different contexts.

But let's get back to the first sentence. Many people would advise you that is preferable one compliment than an apology, so we could redo that sentence into:
" I thank you for your patience."
I would like to thank you for your time and patience.
I really appreciate your help and taking the time to listen, etc.
Thanks for listening. (they took their time to listen, didn't they? - it could be expressed to a friend).
Thank you for your time today.
Thanks for your collaboration/teamwork here (to a coworker/employee, etc)
I am thankful for your support and understanding.

I am sorry for any inconvenience this/we/I may have caused you. ("inconvenience" sounds 'business', that is - a bit on the formal side here).

And other ways, it goes with the emotion, the feeling, perhaps.