Batteries are selected into 2 ways: Application and Construction.
Applications are example Automotive (Starting), Marine and Deep Cycle.
Construction types of battery are Flooded (Wet), GEL and AGM (Absorbed Glass Mat).

Flooded (Wet) battery is commonly use in automotive, with the removable cap on top. Must stand upright and produced gas when
charging. Design to discharge only 5% and normally in fully charge condition. Life span is about 2 years in a car.

GEL battery is a sealed type with the Silica Gel added to the acid. Advantage compared to flooded is the acid will not be spilled out even if the battery is broken. Deep cycle gelled battery has the capability of discharge as much as 50% time after time. Current and voltage charging are limited to the manufacturer specification. Specially selected for solar usage with generally 1000 discharge cycle at 50% dischage.

AGM (Absorbed Glass Mat) Deep Cycle battery uses fine fiber Boron-Silicate glass mat between the plates. Do not have strict charging voltage or current limitation. Suitable for all general usage. Have a life of 500 discharge cycle at 50% discharge.

Life span of battery has a few years variation range. This is due to battery type and usage, depth of discharge, temperature, etc.
Lastly is the brand and quality. The golden advice is "You always get what you pay for".

TIPS to prolong the battery life:
1. Ideal battery bank is a simplest, consisting of a single series of cells. Higher capacity batteries tend to have thicker plates and
longer life.
2. Under no circumstances to install more than 3 parallel battery strings. More batteries will tend to lose the equalization resulting in
accelerated failure of any weak cell. The weak cell will "steal" the energy from the surrounding cell causes invisible energy lost.
3. Maintain symmetry in wire size and length will help to distribute current evenly through the bank. All the batteries in the string will
be evenly charged.
4. Maintain even temperature distribution to the battery bank and avoid uneven exposure to heat source. Temperature will effect the
charging characteristic. Leave at least 0.5 inch of air space evenly around each battery for cooling.
5. Fully charge all the batteries with external power every 3 weeks.
6. Not advisable to enlarge a battery bank by adding new batteries to it. Because batteries' voltage response changes with age. Stray current flow will cause losses and failure to equalise.