How long can I safely maintain a 1000 calorie deficit?

Congratulations on your success thus far! I started out at about 220 also and am currently hovering around 178, but that is after losing down to 162 and then gaining some back (I am currently working on getting it back off).

Everyone is different, but here is my story and you can take it for what you want....while I was actively losing weight, I ate around 1200-1500 per day and exercised 2x per day so that my net calories (calories ate minus calories exercised) was around 900-1100. I did this for about six-eight months and continued to lose consistently throughout - no major plateaus.

The drawback to this plan was that, for me, that level of exercise was not sustainable long term. When I backed off on the exercise (and maybe started eating a little more), I gained some of the weight back. The upside was that I lost the weight fairly rapidly and that kept me very motivated.

So now I am working on finding the right balance of calories in and out that works for me. I am not exercising a lot right now, focusing on maintaining or slightly losing by controlling what I eat. I plan to add in exercise once I get control of my eating habits, but at a level of 30-40 mins, 3-4 times per week.

Again, I am sure you will get some great advise here on mfp, there are a lot of great people who have had great success. I encourage you to thoughtfully consider their experiences, but listen to your own body and follow your instincts as to what is healthy and works for you. Best wishes.

Here's a chart that floats around..........

If you have 75+ lbs to lose 2 lbs/week is ideal........ (this is a 1,000 calorie deficit)
If you have 40-75 lbs to lose 1.5 lbs/week is ideal,
If you have 25-40 lbs to lose 1 lbs/week is ideal,
If you have 15 -25 lbs to lose 0.5 to 1.0 lbs/week is ideal, and
If you have less than 15 lbs to lose 0.5 lbs/week is ideal.

You step it down because moderate weight loss (for your size) helps you lose fat....as opposed to fat+muscle.

you don't need to...................750 is better.....the closer you get to your goal, you won't be able to maintain 1000.......if you aim for 1.5loss and workout 5-6 days a week. then you're on a 2-3lb loss pace

I am 5'11", 205 lbs, and 27 years old. I started dieting at a 1000 calorie deficit 45 days ago and have lost 15 pounds as of today (I started at 220). My goal is somewhere in the 170-180 range. MFP has me eating 1,410 calories per day to continue losing 2 lbs per week. I ride a stationary bike three times per week, burning around 500 calories each session (according to my heart rate monitor), and eat back anywhere from 50-75% of those burned calories.

Right now I feel fine, but will there come a time where I will need to change to a smaller deficit in order to stay healthy?

Congrats on the weight loss! But.......1410 calories! Damn! Of course you are losing weight. I would not go lower than that. You should start lifting heavy.

1410 and MALE :noway: ............1410 is about right for me and I'm female & 5'5"

You already need a smaller deficit. Google skinny-fat