Creaking sounds from the saddle tube? I've started to hear creaking/clicking sounds from the saddle tube. Is the frame giving up?
I could look for a longer saddle post, if that would relieve some of the strain on this part of the frame, but I'm not sure what length to get. 

I've measured the outer diameter of the post to be approx. 27mm -- but what is the proper name/size for this dimension?

It's a 58 (cm/in?) aluminum frame with 28" wheels, roughly 10 years old. I've got the saddle fairly high, but I'm a tall guy (192cm, 95kg) so it needs to be like this. When I put a heel on the lowest pedal, my leg is practically straight. Perhaps I should buy a bike with a bigger frame, if that exists, but I am hoping to avoid significant expenses. The bike is otherwise in good condition.

Updates to comments:


Saddle post is 1cm lower than its "max" mark. Close, but okay - perhaps too close, given my weight? (95kg)
frame and post is metal, presumably both aluminum.
Creaking goes away when standing. That's why I suspect this area.
Saddle clamp and rails seem good on visual inspection.
Often, dirt gets between the seat post and seat tube. Remove the seat post. Clean the post. Clean inside the seat tube. Grease the post and re-install. Hopefully the noise will be gone. You say the post is close to the max mark. For a little added safety, longer seat posts are available.