Plants can be kept in containers longer than they should be for maximum vitality. Often, leaves appear perfectly healthy, but shoot extension decreases as root congestion increases. So, if shoot extension decreases from one year to the next, you have a plant with deceptively healthy looking leaves that is really in a state of decline. Remedy is a repot in spring before buds break. Also look to the drainage hole for clues. If roots are growing at or out of the drain hole, or if they are climbing over the soil surface, a repot should be in the plant's near future. If not, and soil is draining well (a L. requirement, as you know) you should be good for another year.

Good luck.

Al