Make sure you have a controlled current to make your silver! I have used both a rigged up stirrer and a magnetic/heater lab one, not much difference. Nice to have but not have too.

The most likely answer is, that it helps.

In a nutshell... stirring reduces agglomeration during processing. This promotes the dispersion of the silver ions which in turn adds stability to your final solution. ie, Without stirring, I've estimated my saturation limits to hover at/or around the 16ppm mark. Whereas the same process settings run with stirring allows for slightly higher PPM(+2) along with added stability in terms of storage.

Which works out to be at/or around 18ppm in my own case: via physical and theoretical contrast measurement..

And so, the going consensus is that stirring reduces agglomeration and helps disperse the field strength between ions as they form in the solution. One easy way of gauging the effects yourself can accomplished by taking current readings with and without stirring. ie, disconnecting the circuit, waiting a few, then taking note the resistance and/or conductivity in your solution. The comparing the same with stirring.

That being said, some the more common stirring methods are; air bubbling, thermal agitation(convection), magnetic stirring, and water circulation via a pump.

Personally, I've tried many methods, but the magnetic stirrer proved to give the best results. Then again... I'd add that my own personal requirements are likely far too critical for most. Though it remains, that every other method safe the magnetic stirrer ended-up introducing contaminants in the solution. And so there's that to consider I suppose.

Hope this helps

The SilverJoe Cell for making Silver solutions is required to be stirred Anti clockwise.
The left rotation of fluids causes the fluid to take on a positive energy field thus enhancing the effectiveness of the solution.
This has to do with the earths magnetic fields and interactions