When do Labs Come into Heat?

Usually around 6-9months.

Hopefully she'll never come in to heat - please get her spayed.

There's a lot of false information out there - that it's supposedly healthier to let her have a litter of puppies first (it's not) or that spaying is somehow interfering with nature in some bad way. Take a look at the shelters - they are full. There is no need to keep adding to the huge numbers of dogs who are homeless. Additionally, since I see that you are concerned about cancer, it will interest you to know:

"A female dog spayed before her first heat will have a near zero chance of developing mammary cancer. After the first heat, this incidence climbs to 7% and after the second heat the risk is 25% (one in four!). It is easy to see that an early spay can completely prevent what is frequently a very difficult and potentially fatal form of cancer. "

from

http://www.veterinarypartner.com/Content.plx?P=A&A...

They can be as young as 6-7 months of age but usually they're a bit older, like 8-12 months of age.

If you're considering spaying her, have it done when she's 6 months old. There is NO benefit to letting her have a heat cycle first. Spaying before they ever have a heat cycle reduces their chances of developing mammary cancer later in life by 98% (in other words, she only has about a 2% chance of developing breast cancer if she's spayed before her first heat cycle). If you wait until she's had one heat, her chances go up to about 20%.

6-9 months of age.