Jeep Repair: AC & Slight Missing while driving, cherokee sport, ac works

Question
QUESTION: First, the AC blows cold for about 15 mins. then gets warm.  Been told by a local shop it is the evaporator needs to be replaced. Second, while driving on the hwy, spd ctl on, it feels like the jeep is missing every once in awhile.  Thanks for taking the time to look at my questions.  God Bless

ANSWER: what kinda jeep is this  and engine size.

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QUESTION: 2000 Cherokee Sport 2dr, 4.0 liter engine, 130,000 miles

Answer
an evap is a hard part with no moving thing in it  so all it can do is leak  either the ac works  or not   if the evap was leaking  after the freon is all leaked out  it wont get cold at all    not work for 15 min then stop working.   U could be looking at a compressor,a sensor or a clog in the line  something along that lines.
As for missing  how do u know its missing  do u have a check engine light on with misfire codes?