Does the rewards for praying in Masjid al-Haram count for future prayers?

If someone prays ONE prayer in Masjid al-Haram, then the reward is 100,000 prayers. If that's the case, then does it mean that it will cover up 100,000 prayers in the future or just past prayers? The reason I ask is: Someone went to Mecca recently and prayed in Masjid al-Haram and then came back and told me that they don't have to pray because the prayers they prayed in Masjid al-Haram counts for a lifetime. Is that true? Thank you.