Bilal i would like to talk with that friend of yours who thinks rapid oil change can reduce engine life hehe :p...
Now with oil changes there is a big difference between a engine of car and a motorcycle engine...
Now whats the difference, a car engine normally have a RPM of around 8 and a bike have an rpm of 12-14 now bcoz the Bike engine is a high revolution engine the oil loses the viscosity or u can say its thickness way before a car engine and bcoz our bikes here uses the same engine oil in gears as well i mean in all our local bike the mobil oil also lubes the gears and gears makes the engine oil contaminate then we have a wet clutch plate system now wet clutch plate system means the clutch is dipped in the oil and that also contaminate the oil way sooner than car engine..
car engine have separate oil for gears and a dry clutch plate system so if ur changing ur bikes oil like car than i m afraid it might last but when u will go for a rebuild u might have to change a lot more things than a person who is changing oil regularly and on time..
Engine life totally depends on oil if u can afford change your oil after every 1000Km and the max u can is 1500 Km above that isn't recomended....
When u go for 1st tunning change ur oil and a new engine bcoz its new the grinding of new parts produces more contamination than an old engine thats why u have to change the oil of new engine 2 or 3 times before the running completes...
Always use good oil i use Castrol GTX people say caltex havoline is good but i have experienced bcoz the bike engine produces a lot more heat the Havoline starts to fail at around 800km the oil starts to reduce a bit plus if u push ur bike really hard u can smell the burning oil...
Now the choice is yours i would recomend you should change your oil on 1000. then u should change it at 1600 Km bcoz the suzuki engine breaks in late u should change it at 2000 KM and after that every 1500 Km and Oils if u can find Total Quartz 5000 Oil that will be best 1 liter casts 230 but its the best oil and latest but the 1 liter pack is hard to find if u can find that than go for GTX and than Havoline... always use 20w-50w oil in the bike