The Prophet (may Allah’s peace and blessings be upon him) used to perform ablution upon every prayer

‘Amr ibn ‘Āmir related that Anas ibn Mālik reported: The Prophet (may Allah’s peace and blessings be upon him) used to perform ablution upon every prayer. I asked: "What did you guys use to do?" He said: "Ablution would remain valid for any of us until he broke it."

The Prophet (may Allah's peace and blessings be upon him) used to perform ablution for every obligatory prayer, even if his ablution was not broken. This is to attain the reward and merit. It is permissible to perform more than one obligatory prayer with one ablution, so long as the ablution remains valid.