Ever since the patch was released I've had large mana problems and I'm a fairly geared paladin. I'm still stuck on judging every 8 seconds from force of habit.The first thing you could try is simply to change the key you've bound Judgement too. Perhaps moving it to a different key will be enough to break the habit.
Would you consider any addons to remind or report judging after 30 seconds? Before it was easier because usually after cool down it was easy to judge after 8 seconds (every time judgement came off cool down.)
For keeping track of the Judgements of the Pure buff, I actually use two mods, TellMeWhen and Paladin Beacon of Light/Sacred Shield Tracker.
The second one is a pretty old mod back from when we had to track Sacred Shield and the HoT, but I still use it to track the Beacon and Judgement of Light timers.
For TellMeWhen, I have it set up to display the Judgement icon when Judgements of the Pure either does not exist or only has 15 seconds remaining. I also use TellMeWhen for Holy Shock and 3-pt Holy Power.
Here is the TellMeWhen setup: