It's a valid concern. A single 25 mins block might indeed be too short for a big task but in Pomodoro it's series of such blocks interspersed with 5 mins breaks

It's a valid concern. A single 25 mins block might indeed be too short for a big task but in Pomodoro it's series of such blocks interspersed with 5 mins breaks. YMMV, but I've found out that the 5 mins breaks do not destroy my "state", as long as I don't start anything that tends to suck in like playing games or browsing the Web. Fetching coffee, going to the toilet, etc. is OK :) Anyway, the hardest thing is usually starting the first block.