In case you have problems with your fuel hoses that after 1 year or so they get brittle and start to leak again, you most probably bought the wrong material of fuel hoses. BMW uses for the engine bay and hot spots FKM material, the usual aftermarket fuel hoses are cheaper and are made of NBR. The main difference is

NBR hose up to 100C, FKM to 200C!

FKM grades in the link below from Trelleborg, Denmark, which is one of the major players in seals, hoses etc
Fluorocarbon Rubber (FKM)
In automotive applications , FKM is known in particular for its very good resistance to fuel, oil and aggressive media as well as the excellent resistance to ozone, weathering and ageing. Depending on structure, fluorine content and used curing system FKM materials can differ with regards to their chemical resistance and cold-flexibility. The operating temperature of FKM ranges from -20°C/-4°F to 200°C/392°F, for a short period of time up to 230°C/446°F.

Special FKM grades can be used down to -45°C/-49°F ( XLT grades of Trelleborg Sealing Solutions ).The material has:
•Resistance to oil & grease
•(problematic additives!)
•Very good resistance to fuels
•Excellent heat resistance
•Excellent weather & ozone resistance
•Good acid resistance

Due to high chemical resistance and low swelling in fuels (especially when containing ethanol and methanol) FKM can typically be found in the complete fuel supply chain (fuel injectors, quick connectors, high pressure pumps, etc.). Additionally, gaskets in ECUs for gear boxes are also a field of application.

NBR acrylonitrile-butadiene rubber
NBR has good mechanical properties, low compression set, good low temperature behavior (mix-dependent to -50 ° C) and higher abrasion resistance than most other elastomers. NBR is highly resistant to hydraulic oils, mineral oils, petroleum products and oil in water emulsions, water glycols and animal and vegetable oils, gasoline, flame retardant oil in water emulsion (HFA liquid), water in oil emulsion (HFB liquid) and solution of Polymers in water (HFC liquid). Ozone and weathering resistance is considered poor. Temperature range: -50 to + 100 ° C. Applications: Standard material for oil- and fuel-resistant seals, scrapers and moldings for general applications without exposure to ozone or weathering. The most diverse compounds can also be processed with approvals (eg KTW, DVGW, etc.) or with fabric reinforcements.