Hi!
I want to record all the day in fragments of 10' :
I understand I have to give [writesf~] some time between stop and start to flush everything.
Some seconds before recording a new file I [open( the file.
I have 2 [writesf~] in the patch, so on a bang it records on the first and stops the second, then reverse for the next period.
Am I sure the files finish and start sample to sample?

Then I will [readsf~] them in the same way as one stream (12 hours later).

set up some tests where you have a write running and then write a different file at the same time and then stop. while the first is still running. - that should work.
you need multiple writesf objects you can have lots of them and you change the file names with a $1 in the file name / and a counter changing the number in the file name.

the thing should stop on the bang and start on the bang you could check that by counting array samples between start and stop.

It works perfectly with this test:

writesf-test.pd

wow, thank you for this test patch!
I made a flip-flop recorder, now I just have to test. I'll tell you soon...

I'll probably mount the sounds sticked together in a DAW and listen. Then I can make further test to check if we are sample to sample, but if it sounds good, with no clicks, it is enough for me...

no clicks! The junction is perfect. As said, I open next file some time before, and start next file on current file end bang.