I sometimes wonder when bending the rules turns into breaking the rules and from here - when does one say something?

It's a small office. I answer the phones at all times except for the 30 minutes in the morning between 8:30 and 9:00AM (when the office is open but I don't start until 9:00) and then during my 30 minute lunch break which starts promptly at 12:30 as per the boss' request. During these few times, the accountant answers the phone. So what happens when she's away?

Take today for example. Accountant has the day off. I start at 8:30AM and work an extra half an hour (which I am NOT paid for but it is added into a time pool - OK by me). The office manager (who also happens to be one of the owners) is out and about town and in no hurry to "pop into the office". Of course, I can't possibly leave my post. Even for a minute. What this means for me: I've been here nearly 6 hours without a break. No lunch, no coffee, no nature break. Even the most tyrannous boss will allow a nature break no? If this was the first time, I could maybe let it go but it's NOT the first time. It has happened so often that I've lost track.

I only mention this now because I had a late night (2AM I saw the bedroom) and I've had a few cups of coffee and now I need to PEEEEEEEEEEEEEEEEEEEEEEE!