How long before crops in Farmville on Facebook whither away?

I was wondering how long it takes for crops to die in Farmville? I heard that they whither away after the amount of hours it took to grew. So like plants that took a day to grow would die in a day. If they took 4 hours they would die in 4 hours. Is this true?
No rude comments please, I can’t help being addicted to this game.

Yes, the same amount of time it took to grow them, it will take to wither. Raspberries are ready in 2 hours, but you have til 4 hours later to harvest them.

Things that take 3 days, you can harvest them up to 3 days late too.

I hate having withered crops, it makes me sad.

What is the best deal on Facebook FarmVille?

I was just wondering which is the best deal for the crops on FarmVille.
Which has the most profit for the less time and things like that.
Oh, and if you would be so kind as to add the formula since school is starting soon and I need to learn that.

-Assume fixed number of units
-Time interval is controlled
-Experience gained per harvest not included

Sample Calculations…

E.g. Strawberries
Revenue per unit = 35 coins
Cost per unit = 10 coins
Profit per unit = 25 coins
Harvesting period: 4 hours
Profit per day for 1 unit (Assume ideal harvesting times):
(25 coin profit – 15 coin plowing) x 6 harvests per day = 60.00 coins

E.g. Eggplants
Revenue per unit = 88 coins
Cost per unit = 25 coins
Profit per unit = 63 coins
Harvesting period: 2 days
Profit per day for 1 unit (Assume ideal harvesting times):
(63 coin profit – 15 coin plowing) x 0.5 harvests per day = 24.00 coins

E.g. Wheat
Revenue per unit = 115 coins
Cost per unit = 35 coins
Profit per unit = 80 coins
Harvesting period: 3 days
Profit per day for 1 unit (Assume ideal harvesting times):
(80 coin profit – 15 coin plowing) x 0.33 harvests per day = 21.60 coins

E.g. Soybeans
Revenue per unit = 63 coins
Cost per unit = 15 coins
Profit per unit = 48 coins
Harvesting period: 1 day
Profit per day for 1 unit (Assume ideal harvesting times):
(48 coin profit – 15 coin plowing) x 1 harvest per day = 33.00 coins

Remaining seed types…

Squash
Profit per day for 1 unit: 33.00 coins

Pumpkin
Profit per day for 1 unit: 69.00 coins

Artichoke
Profit per day for 1 unit: 29.75 coins

Rice
Profit per day for 1 unit: 72.00 coins

Raspberries
Profit per day for 1 unit: 132.00 coins

Cotton
Profit per day for 1 unit: 39.00 coins

Peppers
Profit per day for 1 unit: 77.00 coins

Pineapples
Profit per day for 1 unit: 66.00 coins

Blueberries
Profit per day for 1 unit: 156.00 coins

Watermelon
Profit per day for 1 unit: 50.75 coins

Potatoes
Profit per day for 1 unit: 65.00 coins

Corn
Profit per day for 1 unit: 71.66 coins

Sunflowers
Profit per day for 1 unit: 165.00 coins

Different seeds yield different amounts of experience-gain. Hence raspberries yield 0 experience-gain but is rewarded with high profit.