Go to gameserver/data/stats/skills and open the files there and find the buffs you wanna make more time and then change the time like that :
<skill id="1240" levels="3" name="Guidance" enchantLevels1="30" enchantLevels2="30" >
<table name="#enchantMagicLvl"> 76 76 76 77 77 77 78 78 78 79 79 79 80 80 80 81 81 81 82 82 82 82 83 83 83 84 84 85 85 85 </table>
<enchant1 name="magicLvl" val="#enchantMagicLvl"/>
<enchant2 name="magicLvl" val="#enchantMagicLvl"/>
<table name="#ench1time">
1240 1280 1320 1360 1400 1440 1480 1520 1560 1600
1640 1680 1720 1760 1800 1840 1880 1920 1960 2000
2040 2080 2120 2160 2200 2240 2280 2320 2360 2400
</table>
<table name="#ench2MpConsume">
40 39 38 38 37 36 36 35 34 34
33 32 32 31 30 30 29 28 28 27
26 25 25 24 23 23 22 21 21 20
</table>
<table name="#ench2MpConsume_Init">
10 10 10 10 10 9 9 9 9 9
8 8 8 8 8 8 7 7 7 7
7 6 6 6 6 6 6 5 5 5
</table>
<table name="#mpConsume_Init"> 7 9 11 </table>
<table name="#mpConsume"> 28 35 41 </table>
<table name="#Tab-accCombat"> 2 3 4 </table>
<table name="#aggro"> 379 457 532 </table>
<set name="mpInitialConsume" val="#mpConsume_Init"/>
<set name="mpConsume" val="#mpConsume"/>
<set name="power" val="0.0"/>
<set name="target" val="TARGET_ONE"/>
<set name="reuseDelay" val="6000"/>
<set name="hitTime" val="4000"/>
<set name="skillType" val="BUFF"/>
<set name="isMagic" val="true"/>
<set name="operateType" val="OP_ACTIVE"/>
<set name="castRange" val="400"/>
<set name="effectRange" val="900"/>
<set name="aggroPoints" val="#aggro"/>
<enchant2 name="mpConsume" val="#ench2MpConsume"/>
<enchant2 name="mpInitialConsume" val="#ench2MpConsume_Init"/>
<for>
<effect name="Buff" time="7200" count="1" val="0" stackOrder="#Tab-accCombat" stackType="accuracyUp">
<add order="0x40" stat="accCombat" val="#Tab-accCombat"/>
</effect>
</for>
<enchant1for>
<effect name="Buff" time="#ench1time" count="1" val="0" stackOrder="4" stackType="accuracyUp">
<add order="0x40" stat="accCombat" val="4"/>
</effect>
</enchant1for>
</skill>
and change the thing in red