Any fabric or leather will need cleaning from time to time. It's a fact of life.
Any natural fibre fabric will be subject to staining because they are absorbent to both water and oily soils. Applying a protector is a great idea as it makes the fibres less absorbent and makes it easier for you to blot up spills and helps keep soil on the outside of the fibre, rather than letting it soak in where it can cause permanent damage.
Don't rely on the store applying the protector. Have it done by a professional carpet cleaner. Check the WoolSafe Website for the location of a fully accredited carpet cleaner near you who will do it for you in your home so that you can see it is being applied correctly.
I have been on many a loading dock and seen the storeman spraying protector in the general direction of a lounge and putting on about 1/3 of the amount required to protect it.
By the way most of these protectors are very similar. Only about 5% of what is sprayed is the floropathic resin that does the actual protection. THe rest is carrier (water or solvent). If you decide to spray it yourself, you need about a can and a 1/2 for each seating position to be applying an effective soil barrier.
Incidently, they work by using the surface tension of the liquid in the spill. The flourochemical that adheres to the fibre is inert so nothing wants to react with it. It doesn't form a layer of 'Glad wrap' around the fibre so it still breathes and feels as it originally did. It is now just less inclined to absorb liquids into the fibre. An open weave fabric will still allow the fluid to pass straight through. It will still get dirty over time but when it is cleaned it should clean much better than an un-treated lounge.
Warranties differ a bit, but basically you are still responsible for cleaning and maintaining your lounge for the warranty to remain in place. There is usually a clause in there that states something like "...if there are any stains remaining after professional cleaning then the company will pay for the cleaning of the stain only." Not much of a warranty really. As well as that you will find there are exclusions to the warranty such as ink and paint etc. Some even exclude hot tea and coffee.
If it is protected well, then the marks will clean out by the professional cleaner and therefore leaves nothing for the warranty anyway.
Leather is a whole other animal (pardon the pun). The leather in the picture looks like it is a pigmented leather. There are dozens of different finishes for leather. Some are absorbent to sweat and soils and some are not.
A pigmented leather has been tanned, split, dyed and a few other processes, and then painted with a layer of paint they refer to as pigment. Usually there is a fine layer of polyurethane over the top to protect the paint from damage by the sweat. If it doesn't have this layer of urethane then you need to apply this yourself by applying a protection creme treatment. Fenice, Leather Master or Pelle would be the three brands I would reccomend.
Don't use wax or sadddle soap or any of the home brand recipies. Remember, you are not cleaning leather, you are cleaning the urethane coating on the top of the pigment which is on top of the chemically preserved leather underneath.
Aniline, nubuck and suede leather are in the absorbent category and these are much harder to clean. They do not have a pigment layer or the urethane to help protect it. For these I would reccomend professional cleaning by a leather specialist only.
But to maintain any of the above, use a barely damp microfibre cloth and wipe over once a month on the body contact areas. Then have it professionaly cleaned about once every 12 -18 months. With a pigmented leater, the cleaner will re-apply the protection creme to keep the urethane in good condition. The urethane is only a few microns thick and wears out over time. Once you have worn through it, the sweats and soils pentrate and damage the pigment and that is the beginning of the end of your lounge.
Leather doesn't need to be 'fed'. The poor animal ended up at Maccas a while back, but in respect to the proud animal that once lived in your lounge, we need to honour it's life by maintaining the leather in the best condition possible. To do thi s, the urethane protection needs to be kept flexible or cracking starts to happen. This is the second job of the protection creme treatment. It helps keep the urethane flexible and this helps prevent the cracking.
As far as warranties on leather treatments go, they often do nothing to the lounge at all. They call it a "dry warranty". They put your money in a bank account and if you have a spill, they pay someone to go and fix it (if they can).
Which ever you buy , leather or fabric, you have to maintain it if you want it to last. They will cost you around the same to maintain.