• Matplotlib version, Python version and Platform (Windows, OSX, Linux ...)

Python 3.5.1 |Continuum Analytics, Inc.| (default, Dec  7 2015, 11:24:55) 
[GCC 4.2.1 (Apple Inc. build 5577)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import matplotlib
Vendor:  Continuum Analytics, Inc.
Package: mkl
Message: trial mode expires in 29 days
>>> matplotlib.__version__
'1.5.1'

• How did you install Matplotlib and Python (pip, anaconda, from source ...)

Conda.

• If possible please supply a Short, Self Contained, Correct, Example
  that demonstrates the issue i.e a small piece of code which reproduces the issue
  and can be run with out any other (or as few as possible) external dependencies.

%pylab notebook
plot([1,2,3])

• If this is an image generation bug attach a screenshot demonstrating the issue.

No

• If this is a regression (Used to work in an earlier version of Matplotlib), please
  note where it used to work.

Not sure, hadn't noticed.

Issue specifics

If I create any figure with the notebook backend, and I switch away from the open notebook to some other work, invariably after returning to the open notebook a few minutes later I find my interactive figure closed (replaced by the static png render).

Is this intended behavior, is there a timeout somewhere that can be used controlled, or is it a bug?

Thanks!