Good point about stamina but still, when Yoda immersed himself in the Force, he bacame young again.
I have a few more theories. My opinion is that Palpatine managed to kill three masters so easily not just because of his uber saber skill. As Sith he was master of exploiting enemy's fears and doubts. Those masters simply weren't ready to face a Sith Lord and Palpatine used their fear to numb their movements. Just like in Dark Nest, when Lomi Plo used Luke's fear for lives of Mara and Jasen to freeze him in place completely and it was Luke in his prime.
No matter how powerful Palpatine was, as any Sith he was coward. He felt Windu's determination and self-control and couldn't expose his emotions and as result he got scared himself even more.
With Yoda situation was different. Turning Anakin to darkside, issuing Order 66 and achieving what no other Sith could gave him exhilaration of victory making him much stronger.
About Palpatine rarely using lightsaber is not entirely true. He started heavily abusing Force only after establishing Empire. He increased his power so much that his body couldn't contain it and started failing.
^ As far as I know Palpatine had not touched his lightsaber for about 10 years when it came to the time of ROTS. I think other posters on these boards have previously posted evidence of this. Might be from the ROTS novel.
As for why Mace could challenge Sidious whilst the other Jedi could not.. Lucas was asked about this and he responded: "You have to be Mace or Yoda to compete with the Emporer. Anakin could have defeated the Emporer had he not got all beat up." (Making of ROTS). So only those people could possibly have competed with Sidious, no one else.
As for Yoda immersing himself in the Force to become young again.. Dooku does a similar technique every time he got tired against Anakin and Obi-Wan, but it was dependant on his Force reserves.
Thats why Anakin has such good stamina, because he basically has an unlimited amount of Force reserves to draw from. Of course Yoda will have a decent amount of Force reserves to draw from as well.
I actually don't know about Palpatine before RotS, I made an assumption since he trained Maul. Logically to fight Yoda on equal terms he obviously should have had some practice.
Are there actually situations in novels, where Anakin got exhausted from using too much Force?
As far as I know He did used to train with his Saber at the time Maul was his apprentice, and he wasn't too busy being Supreme Chancellor and instigating a Galactic civil war. But that was all 10-13years pre-ROTS.
Anakin doesnt get tired. He actually gets stronger as the fight goes on, due to his virtual limitless Force reserves to draw from.
It’s been stated that anakin was in his physical prime in ROTS and being confirmed as one of the most powerful force wielded in history. Zone anakin would utterly shit stomp Malgus.
__________________ "Happiness is a lie. Life is horror. The light is always dying all across the universe. The last star will flicker out someday, when it does, all that remains is shadow. And I will be its king!"'-Amahl Farouk