Depends on the developer really. Also the dilution. Dektol straight should
keep for a month or longer.

Regards,

   John - Photographer & Webmaster
   Website - http://www.darkroompro.com
   Please delete the "_" if replying by mail.

 I'd say weeks if Dektol or Agfa 100 were in place and not used.
Depending upon which developer is used and it's dilution the amount
of time might be from minutes to months.
 The narrow slots with a lid in place admit very little air.   Dan

I use an older style of Nova for B&W work and when I'm using it
sporadically (i.e. not exhausting the chemicals) I get at least 4
weeks out of Agfa Neutol WA (standard dilution 1+7) and Agfa
FX-Universal Fixer (1+6).  When using the setup more frequently, I
drain a bit and top up with fresh at the same dilution(I just estimate
that I've drained about a fifth of the volume from time to time, no
calculations).

I have an idea that the Kodak and Ilford print developers don't last
as long, but I don't remember where I heard it.

I looked at the FB model, but I prefer the older one because it's
narrower (I have a small darkroom) and the frames used to hold the
paper in the FB model are expensive if you want to use several (and
for one paper size only).  With the older style paper clips, I use two
(and two hands) for paper over 8inch x 10inch (fibre paper), and they
hold the paper in the archival washer too.  I lashed out and bought a
number of the clips.  When I need more clips, I change the clips of
the paper in the washer to stainless steel dental film clips.

I have used a 30 x 40 cm 3 slott colour processor with black and White
Chemistry, Ilford M;ultigrade developer an Ilford Paper fixer. I emtied
it after six weeks, but it was still working fine. Therreason for
ewmtying was at was going away on holloiday. I Have heard thar chemicals
should keep 2 months, if the slots are kepr full (So the lids get wet
when applied.

Regards John Dancke