DEF light on my 2012 Solera came on at ~4300 miles. I understand (from posts on this forum) that starting in 2012 Soleras have smaller DEF tanks. Allows an added storage bin. Mine took 9 quarts to fill. From my experience and another post on this forum, I believe DEF consumption is about a quart every 400 to 500 miles.
I was able to have the DEF refilled at JiffyLube. Charged about $10 per gallon installed. I have also seen DEF by the gallon at Camping World. Important, I understand from JiffyLube, to use a "new, dedicated" funnel to add DEF.
To get the indicator to reset after filling the DEF reservoir, I found I needed to turn the key until all indicators lit, wait in that key position (WITHOUT starting the engine) until the indicators (including the DEF indicator) went out, then start the engine.