Come on you guys seriously?
Spock attempted Kolinahr twice. It takes years to complete. First attempt start date 2270-2273. Not complete.
He started his second attempt after Captain James T. Kirk dies in the Nexus star date 2293. After years he did complete Kolinahr, only to start the process of reversal after Doctor McCoy enlightened him of the importance of grieving his mothers death.
Sources (
1,
2 &
3 )