Determine avarage steady state of multiple data sets

I have sets of data which when plotted look like this:

How can determine the "avarage" value these 3 data sets flatten out on? In other words, the average "steady state" of these three data sets.

By eyeballing it I can estimate that the average steady state is 4.5N but I'm hoping that there is a nice matlab toolbox (I have them all installed) or another method.

Note: This is Force vs Time.

[dpb]

I'd probably start by looking for the increase above the end value of some percentage and then try some heuristic tests of fitting a linear slope and look for departure of residuals to begin.

If it weren't for the tendency to have a rise at the end might work to fit a breakpoint model to the plateau and discover the change point as illustrated in a previous response. Would work pretty well for the orange I think; not so sure w/o trying on the blue but still might be good starting point...

http://www.mathworks.com/matlabcentral/answers/164913-difficulty-in-fitting-two-lines-with-polynomials

I showed piecewise regression in second answer to above query...

ADDENDUM

Might be simpler to see if were to normalize the x axes to align the peaks as the peak width seems to be pretty consistent duration.

[dpb]

Can you attach the dataset?