Long baths can open up your pores and remove oil from your skin, so after your bath remember to put on moisturizers like cocoa oils, moisturizer butter to ensure that your skin doesn't dry out. If possible try putting your creams next to your bath or heater to make sure they aren't cold to the skin.
Bring in your favorite book and a glass of wine with you. Wine can help relax you, but be careful not to fall asleep. Reading in the bath can be fun as well, you'll not even notice the hours pass by!
Turn off your phones both your land lines and your mobile phones. If you have pets feed them and put them outside if possible. Tell the rest of the household (if any) that you are going to relax in the bath for a couple of hours and make sure you clear your appointments. If time is really short, set an alarm to tell you when you need to get up, nothing is worse than looking at your clock every few minutes!
Having a hot tub is nice, but most people don't have the luxury of the space or time to install a new hot tub or spa tub. Consider buying a spa mat, that goes into your existing tub. Before you buy note that some brands can be loud, do your research and this could be a relatively inexpensive way to feel like you're in a spa tub.
Consider using bath oil, bath milk, bath salts, bubble baths, fizzling bath balls. If you haven't tried all these combinations try them and find out which one suits you. Also consider putting in a few drops of essential oils like lavender, eucalyptus, rose, jasmine and bergamot.