Darryl’s Analysis

Environment:
Although I can’t see exactly where the window is in the photo, I can tell there must be a large one to the right (perhaps a patio door).  If you’ve had the plant for 3 years, then it must be fine in terms of light.

Effort:
RED FLAG – the soil you have used looks like mud.  Houseplant soil is generally composed of a fibrous, water retaining component (like peat moss or coconut coir) and a drainage component (like perlite, bark chips, or coarse sand) – it should be somewhat loose and gritty.  A soil so dense like this will severely limit airflow to the root zone and put them at high risk of root rot.

Expectations:
Other than the soil situation, the overall plant looks quite healthy so far.  Once you’ve owned the peace lily for the long term (I’ve had mine for 8 years), you’ll get accustomed to the usual rate of leaf turnover, which may not occur until a few years into the relationship.  I wouldn’t be too concerned about a few browned tips or patches – just cut off the leaf once it’s fully dead.

Here’s my plant before removing dead leaves and after – I have to do this every few months:

Older leaves will eventually get browned tips:

The youngest leaves will have nice, pristine tips.  After a few months (or maybe a year or so), they’ll eventually become brown as a result of filtering minerals – just the wear and tear of hard work.  As long as the plant is pushing up new leaves to replace the old ones, I’m happy with the plant.

Learn my long-term enjoyment approach to houseplant care – learn from my course.