I do think that with the medicals checks and the required training age is not really issue any more, except that it might indeed take longer.
A friend of mine who is instructor (gliders) at EBZR told me that on average (!) for every year above 25 he needs to teach about 30'~1h in extra flying lessons compared to those of the 18~25 years old bracket. However, he also noted that lately there are more and more exceptions to this.