What is the cutoff period (eg. months, years) after a network
marketing company is established (with revolutionary technology and a
new delivery method) for one to join if maximum income levels are to
be reached?

If you look at purely the maths, first in best dressed.  The REALITY
is though that 'most' who become involved do not do the work required
to become successful or wealthy.  If there is 'downflow' from an
'upline' make sure you understand how that works or how it is
directed.  I think you will find all are structured so that he who
does the work, can indeed reap the benefits.  Pyramid schemes (purely
maths and the first guy gets rich) are I think illegal for precisely
that reason.  Recommend RESEARCH RESEARCH RESEARCH both your product
or product base, is it renewable/resellable/consumable?  Does it rely
on finding 'new blood' the whole time?  Consumables tend to stick
around for a while, new blood rarely for long.  Be careful of monthly
fees you might have to pay, whether that be for 'site priviledges' or
other commodities designed to 'help' you.  Often thats where they
actually make their money, out of you buying those services.  If you
are prepared to do your own marketing for a valid tangible product,
and work hard, you will make the money you generate.  There is not
easy street.  Like anything, look, learn, and think hard, and work
even harder.  And you need to market the idea as much as the product
in order to build a network.  In order to do that, you yourself have
to be comfortable with the fact you have what it takes.  Good luck
with your venture.

Generally, I've heard the 5 year mark to be one to trust, since so
many NWM companies fail within the first five years.  You want a
company with a significant track record of success, and there are a
few who have this prior to that five year mark.  Also, even within the
company, getting connected with a strong, active, and growing TEAM
within the company is another VERY wise consideration.  I never had
significant success until I alligned myself within a team of
successful people, many of them are already top earners, including a
few millionaires, and we're not yet at the five year mark with this
particular company.  Many of us met within a prior company, and are
already having better success as a whole than many others.  It's all
about teamwork, being in business FOR yourself, but not BY yourself,
so be careful which individuals you align yourself with.  Keywords: 
teamwork, leverage, residual income, high demand products, integrity,
ACTION!