I grew up putting a crushed aspirin into the water of the tree stand to help our tree last for the season and prevent needle loss. Turns out... this is an old wives' tale! Aspirin does have benefits for growing certain plants (scientifically proven!) but as far as helping your Christmas tree stay fresh, not so much. Other additives that also do not work are corn syrup, bleach, baking soda, 7Up, and sugar. What your fresh Christmas tree needs the most is WATER! Be sure to keep the trunk submerged in at least 2 inches of water and use a large basin tree stand. According to the NC State Extension, trees can take up to a gallon of water the first day or two.
Other tips to maintain your tree:
Cut at least half an inch off the bottom before placing in your tree stand (Pinterest hack... use that piece of wood to make a commemorative ornament for the year)
Do not place near vents
Be sure to turn off tree lights before going to bed
Avoid keeping your tree near entryways or doors. Sudden changes in temperature are bad for the tree
A humidifier might help, especially in dry environments