Trading a tub for a walk-in shower makes your bathroom feel larger and safer for the long haul. Most contractors finish this work in about a week, but the real benefit is the daily ease of getting in and out without a high ledge to clear.
January is the best time to book your project. Contractors are often looking for work after the holidays, so you might get a better price or a quicker start date than you would during the busy spring season.
The 18-month window is a tool for spreading out your costs, not free money. If you have a remaining balance after the 18 months are up, the interest charges will hit your account, so stick to your payment schedule.