Do you think 'practice makes perfect', or 'practice makes permanant'?
It is surprising how many of my clients do not have a practice plan. This inevitably means you are practicing faults and grooving them, rather than sound principles.
The earlier in your golfing life you learn sound principles, the better - sound mechanics are important to be able to play the game consistently well. There are a number of issues that have to be taken into account: your range of motion, the time available and the incentive. If necessary get professional help to form a practice plan, which has clearly defined goals that are specific, measurable, achievable, recordable and timed.
Playing 36 holes in a weekend, every weekend, may not be the best approach to improving your golf. By playing only 27, put the time you've saved into a practice session which is planned out. Include the 9 holes missed from your orginal 36, to actually transfer the practice from the driving range or short game range to the course.
Fellow of the Professional Golfers' Association