Hmm, the plan aims to get you to running for 30 minutes continuously, or 5Km continuously, by the end of the 9 weeks, or however long you take to get there. Most sessions will be somewhere between 25 and 40 minutes in duration, but depending on the run/ walk periods, your own speed and the terrain that you're running over you'll do a range of different distances. The point is not to run 5Km every session.

It's a progressive development of your capacity and capability, with some of the effect being the physiological adaptation to running in your muscles, bones and connective tissues.

If you're new to running, but otherwise have a reasonable level of CV fitness, then you clearly have the capacity to repeat the session, but you are exposing yourself to some risk of overuse injury, and compromising your form towards the end of the second session.

It's not a question of not doing it, but you shouldn't need to.

Congratulations on running for 26 minutes straight!

The C25K program is meant to get you running for up to 30 minutes at a time. You won't be able to run 5K in that 30 minutes when you finish the program.
However, you'll have the stamina and ability to increase your time until you can run 5K (you could do it now....it's a mental push to keep running and not stopping). Then, over time, you'll naturally speed up and (maybe) one day you'll be able to run 5K in 30 minutes. I've been running for a bit over a year now and I still can't run 5K in 30 minutes. I hope to get there sometime in the next year. I'm older, though, so it takes longer for me (that's my "excuse", anyway ).
The main thing is to have fun and stick with it. You're doing great.

You won't be able to run 5K in that 30 minutes when you finish the program.

Might be able to...