Read article by Bungie below or @ https://www.bungie.net/en/Help/Article/12287
I PLAYED THROUGH THE WEEKLY EVENTS MULTIPLE TIMES AND STOPPED RECEIVING REWARDS.
Unlike other activities, Nightfall, Heroic Strike, Prison of Elders, Trials of Osiris and Raids use a weekly lockout for earning activity-specific rewards. Players have until Tuesday at 2:00 AM PST/PDT, 9:00 AM UTC to complete any Nightfall, Heroic Strike, Prison of Elders, Trials of Osiris, or Raid activities otherwise their progress will be reset. So what does this mean for these activities?
Weekly Nightfall: Players cannot earn new activity-specific rewards from the activity more than once a week. Separate characters on the same account can each play Nightfall and still get loot; this means an individual player can earn loot from Nightfall a maximum of three times (for three characters) per weekly lockout.
Weekly Heroic Strike: With the release of Destiny: The Taken King, Weekly Heroic Strikes have been changed to a playlist.
- Once per week, players have the ability to earn one Legendary Engram upon completion of their first Heroic Strike.
- Three times per week, players can earn Ten Legendary Marks upon completion of a Heroic Strike. This can be done on a single character, as the rewards for this are account based.
Prison of Elders: There are four different Prison of Elders Arenas, each with their own rewards. Players can earn activity completion rewards once per Arena, per week, per character, but can open the large golden chest for rewards as long as they have a Treasure Key. This means an individual player can potentially earn activity completion loot from the Prison of Elders a maximum of twelve times (for three characters) per weekly lockout.
Trials of Osiris: Players earn rewards based on the number of wins on their Trials Passage. To claim your rewards, return your Passage to Brother Vance in the Reef. Each reward tier can only be obtained once per week, per character. This means an individual player can potentially earn rewards from each tier three times (for three characters) per weekly lockout.
Raids: Players cannot earn new raid-specific loot from a raid more than once a week per mode. The normal and hard mode Raids have their own separate loot tables, so the two modes can be completed separately or can be combined. Completing normal mode does not lock out earning loot on the incomplete hard mode. However, if a player starts the Raid on hard mode and completes it, they will receive the loot rewards from both the normal and hard difficulty mode.
There is a checkpoint for every boss killed that grants activity-specific loot. This checkpoint allows players to return to that checkpoint of the Raid if played before the week resets. Separate characters on the same account can each play the Raid and still get raid-specific loot as they finish each section of the Raid; this means an individual player can earn loot from a Raid for a maximum of six times (for three characters) per weekly lockout. There is a Raid checkpoint tracker for characters that players can access on Bungie.net to keep track of their progress, and to see what bosses have been looted for the week.
You will still gain experience and normal activity engram drops when repeating the weekly events.
^ Source: Bungie