Pressing/Hot Combing the hair is another suitable option for growing out your hair, but there are several major disadvantages:

Excessive heat can cause severe damage to both the new-growth and the chemically treated hair.

Due to a lack of chemicals, you'll find that the relaxed ends will eventually split, become brittle and ultimately break off.

If you go this route, make sure that you do not "fry" your hair by allowing the comb to become too hot (i.e. a "hard Press"). In addition, it's best to cut at least .5-1 inch of the relaxed ends off every month until you're completely rid of it.

Your Natural hair grows an average of .5 inches per month under healthy conditions.  By trimming your hair as it grows, you will be able to maintain a decent length and your hair will appear healthier.  It's also important to keep in mind that due to the curly nature of African hair, it may appear to be shorter than relaxed hair even though it's growing.  

Relaxed hair has been chemically treated so that all kinks, twists and turns in African hair are straightened to their maximum.  On the flip side, natural, untreated hair still has a spring and bounce to it so although it may not appear very long, it's elasticity is high.  Meaning, 5 inches of relaxed hair is really five inches.  5 inches of natural hair, when pulled taut or straightened, can measure 6 inches (or more).

Hot-combing or pressing can last anywhere from 1-2 weeks.  It's at a major disadvantage if you're active or live in a humid climate.  Avoid pressing your hair for an extended period of time (over several months) because doing so will effectively alter your newly established head of natural hair via heat and styling damage.

Despite the negatives, hot combing can temporarily give the sista who longs for lye, a head full of straightened hair without making a permanent commitment.

I have a friend who's been natural for years and occasionally presses her hair for the shock value. She loves the look on her friend's faces when they think she's finally thrown in the towel and decided to relax.

Electric Hot Comb vs. Traditional
I prefer traditional hot combs that have to be warmed in a styling iron stove versus electric ones.  Where electric hot combs allow you to regulate temperature (reducing the probability of damaging your hair due to excessive heat), they do not seem to work very well on coarser hair textures.  Now electric hot combs may have improved since I first when natural so you may want to ask your stylist what brand and model she suggests.

The problem with hot combing is that if you do not do a proper press, you'll find your hair "growing" throughout the day.  I once pressed my hair using an electric comb in the morning.  Everyone had commented on how beautiful, thick and long it was.  See, I still had the Relaxer in...it'd never been cut.

Later that night, I decided to go to a party on campus.  I did a light re-press.  Within an hour of being at the campus party, my beautiful, straight hair had turned into...excuse my language...a hot ass mess!  Yall, I swear it was the most embarrassing moment of my life.  I was so shook.  It's like every step I took towards the door caused my hair to grow.  Talk about embarrassing!  It was at that moment I'd made my decision.  I'm either going to be natural or relaxed...I chose natural.

Long story short, I prefer traditional, non-electric combs.  Where there's a greater degree of user error (letting the comb get too hot), you can get the comb to a temperature that's most suitable for your hair so that your style lasts.  In my case, unlike when I was a child where a press would last about 2 weeks (my childhood stylists knew nothing but pressing hair and could lay it straight without burning or knicking my ears), for some reason as an adult (either due to my technique or the fact that I didn't do "hard" press), my pressed hair only lasted about 2 days. 

In general, some hair textures respond far more to moisture/water/humidity than others.  If your hair is the type to naturally absorb water or "hold water" as my childhood stylist would say (even after drying my hair, there'd still be a degree of water in my hair so that when she pressed it, the steam created by the water would burn her fingers), the quicker your hair will revert to its natural Texture.