I'm coming up on 20 years of active duty service. I am currently an 05 and am on track to make O6. My plan is to serve 30 and walk away and not work again. I would be 52 years old. To accomplish this goal I would need to rely mostly on this pension rather than my current investments.
Is this risky?
Sir - I'm 15 years active duty, planning to serve to my 20 and then out. I am saving to live about half off of pension and half off of savings (interest and dividends generated therein).
I agree that the recent budget approved by Congress and subsequent repeal of the COLA modification gave me real pause. For me, that COLA adjustment would've cost $120,000 over the course of 20 years. There were political reasons I was very upset with Paul Ryan's thoughts on why this was justified, but I won't go into that here.
That said, most politicians and a lot of high military brass agree that military personnel costs are too high and need to be modified. It is my opinion that this means the days of the traditional defined benefit pension are numbered. The civilian force has seen dramatic changes to their pension plans, but they are still quite rewarding.
I believe the likely path for our pension will be that you and I will be fine, and even those serving beyond their first term whenever they decide to make the change will also be grandfathered in with the traditional defined benefit plan. I believe they will change it to a defined contribution system, probably modeled around TSP, which will allow those serving less than 20 to take something of a retirement benefit. I think they will lock in health care for life at 20 to keep that milestone active.
So, all that said, my thought going into a similar retirement plan is that the pension itself is safe. It might get modified, but I don't think that even the COLA adjustment would've been that big a deal, especially considering it reset at age 62 to what you would've been getting all along. Thus, I think our pensions are safe. I think we are going to pay a little bit more for Tricare very soon, so that will affect our spending levels, and should be planned for accordingly.
I also agree with the previous poster who expressed concern over your spending levels. Remember that you won't get 75% of your take home after 30. You're getting 75% of base pay (no BAH, BAS, bonus or special pays). If you have no savings, as you implied in the original post, I believe you are going to be hard-pressed to enjoy your life strictly on your pension. I'd estimate you'll be getting between $80-90K (today's dollars), but if you're truly not saving anything right now, you're spending at least 50% more than that amount.
Perhaps you've been throwing that extra money at a mortgage and your housing costs will be very low in retirement, making that 80-90K doable. It's impossible for us to know how risky your plan is without knowing what your expenses are.
*I* would not be comfortable with only that one income stream (until SS), and have planned accordingly. What you are comfortable with is entirely up to you.