Single vision contact lenses are still the most popular type of lenses available. Most people wear them 2 weekly, monthly or daily depending on their wearing shedule. As a rule I would suggest:
2 weekly replacement lenses
For someone who wants to wear lenses 14 -16 hrs a day 6-7 days a week they are the ideal choice combining comfort with long periods of wear.
Monthly replacement lenses
These are best suited to regular wear up to an average of 14 hours a day 6-7 days a week offering the best combination of comfort and cost
1 DAY lenses
Are by far the best choice for irregular or casual wear offering the best comfort and convenience.