Is it okay for me to supplement with caffeine everyday?

Caffeine can certainly be taken every day...can you say "Starbucks" - some people consume over 1,000 milligrams of caffeine per day from coffee, tea, energy drinks and soft drinks. Some commercial coffee shops serve drinks that have over 500 milligrams of caffeine in one drink (most coffee has a little over 100 mg of caffeine per cup).

Your suspicions are correct though. Your body does get used to caffeine and other stimulants after prolonged use. Ideally, you'd only have your caffeine within 3 hours of your workout, giving you close to 48 hours between doses in most cases. Studies show that subjects who avoid caffeine for several days, get a more potent effect when they re-introduce it to their diet.

If you want to get really serious, you could only take it 2 or 3 times per week before key workouts and then for competitions, stay off it for 4 or 5 days and then take an appropriate dose (usually between 200 and 300mg) about 45 minutes before training.

Caffeine is not harmful to health unless you are one of the minority of people who are sensitive to it. In fact, large reviews of the scientific literature show that people who consume several servings of coffee and tea live longer and have less incidence of disease than those who drink moderate levels or avoid caffeinated drinks.

...also, caffeine increases the use of fat for fuel and moderately increases metabolic rate, so if you are dieting, definitely take it before training sessions and take it throughout the day as a supplement (by itself or as part of a fat-burning supplement) or from tea (green tea is best).